One-Page Checkout [Support Thread]

[schoolboy]

I am having the similar trouble to Nicksab except I am running the following:

Checkout One version 1.0.11
ZenCart v1.5.5
Jquery is 2.1.4
Template is Furniture Black by 12leaves
Using the Gateway Processing Services Module (3-step redirect) for payment (gps.php), CEON module works fine. I'm assuming it just doesn't work with this payment module.

Clicking Confirm Order just reloads the same page. The gateway gets record of the transaction as processing, but it doesn't capture the payment. Never get to the confirmation page.

Debug shows this:

[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined index:  in /home/mcas/public_html/includes/classes/order.php on line 354
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Trying to get property of non-object in /home/mcas/public_html/includes/classes/order.php on line 354
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined index:  in /home/mcas/public_html/includes/classes/order.php on line 355
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Trying to get property of non-object in /home/mcas/public_html/includes/classes/order.php on line 355
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined variable: coupon_code in /home/mcas/public_html/includes/classes/order.php on line 356
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Trying to get property of non-object in /home/mcas/public_html/includes/classes/order.php on line 356
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined index: shipping in /home/mcas/public_html/includes/classes/order.php on line 363
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined variable: pass in /home/mcas/public_html/includes/modules/pages/checkout_one/header_php.php on line 210
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined index: freeshipper in /home/mcas/public_html/includes/classes/shipping.php on line 187
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Trying to get property of non-object in /home/mcas/public_html/includes/classes/shipping.php on line 187
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Constant FREE_SHIPPING_TITLE already defined in /home/mcas/public_html/includes/languages/english/modules/order_total/ot_shipping.php on line 26
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Constant FREE_SHIPPING_DESCRIPTION already defined in /home/mcas/public_html/includes/languages/english/modules/order_total/ot_shipping.php on line 27
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Constant MODULE_ORDER_TOTAL_COUPON_HEADER already defined in /home/mcas/public_html/includes/languages/english/modules/order_total/ot_coupon.php on line 14
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Constant SHIPPING_NOT_INCLUDED already defined in /home/mcas/public_html/includes/languages/english/modules/order_total/ot_gv.php on line 13
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Constant TAX_NOT_INCLUDED already defined in /home/mcas/public_html/includes/languages/english/modules/order_total/ot_gv.php on line 14
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Use of undefined constant MODULE_ORDER_TOTAL_GV_REDEEM_BOX - assumed 'MODULE_ORDER_TOTAL_GV_REDEEM_BOX' in /home/mcas/public_html/includes/modules/order_total/ot_gv.php on line 46
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined index: cot_gv in /home/mcas/public_html/includes/modules/order_total/ot_gv.php on line 48
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined property: ot_subtotal::$credit_class in /home/mcas/public_html/includes/classes/order_total.php on line 165
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined property: ot_shipping::$credit_class in /home/mcas/public_html/includes/classes/order_total.php on line 165
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined index: cot_coupon in /home/mcas/public_html/includes/classes/order_total.php on line 167
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined index: cot_group_pricing in /home/mcas/public_html/includes/classes/order_total.php on line 167
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined property: ot_tax::$credit_class in /home/mcas/public_html/includes/classes/order_total.php on line 165
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined property: ot_loworderfee::$credit_class in /home/mcas/public_html/includes/classes/order_total.php on line 165
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined index: cot_gv in /home/mcas/public_html/includes/classes/order_total.php on line 167
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined index: gv_redeem_code in /home/mcas/public_html/includes/modules/order_total/ot_gv.php on line 238
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined index: submit_redeem_x in /home/mcas/public_html/includes/modules/order_total/ot_gv.php on line 284
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined property: ot_total::$credit_class in /home/mcas/public_html/includes/classes/order_total.php on line 165
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined index: cc_id in /home/mcas/public_html/includes/modules/order_total/ot_coupon.php on line 391
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined index: total in /home/mcas/public_html/includes/modules/order_total/ot_group_pricing.php on line 32
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined index: total in /home/mcas/public_html/includes/modules/order_total/ot_group_pricing.php on line 33
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined index: cc_issue in /home/mcas/public_html/includes/modules/payment/ceon_manual_card.php on line 2933
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined index: gps in /home/mcas/public_html/includes/classes/payment.php on line 175
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Trying to get property of non-object in /home/mcas/public_html/includes/classes/payment.php on line 175
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined index: ResCookie in /home/mcas/public_html/includes/templates/frn_black/common/html_header.php on line 37
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined index: ResCookie in /home/mcas/public_html/includes/templates/frn_black/common/html_header.php on line 147
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined index: ResCookie in /home/mcas/public_html/includes/templates/frn_black/common/tpl_main_page.php on line 45
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined variable: active in /home/mcas/public_html/includes/templates/frn_black/common/tpl_header_top_section.php on line 22
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined variable: active in /home/mcas/public_html/includes/templates/frn_black/common/tpl_header_top_section.php on line 41
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined variable: active in /home/mcas/public_html/includes/templates/frn_black/common/tpl_header.php on line 93
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined index: gps in /home/mcas/public_html/includes/classes/payment.php on line 175
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Trying to get property of non-object in /home/mcas/public_html/includes/classes/payment.php on line 175
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined index: gps in /home/mcas/public_html/includes/classes/payment.php on line 145
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Trying to get property of non-object in /home/mcas/public_html/includes/classes/payment.php on line 145
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined index: gps in /home/mcas/public_html/includes/classes/payment.php on line 175
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Trying to get property of non-object in /home/mcas/public_html/includes/classes/payment.php on line 175
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined index: gps in /home/mcas/public_html/includes/classes/payment.php on line 198
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Trying to get property of non-object in /home/mcas/public_html/includes/classes/payment.php on line 198
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Use of undefined constant CSS_BUTTON_POPUPS_IS_ARRAY - assumed 'CSS_BUTTON_POPUPS_IS_ARRAY' in /home/mcas/public_html/includes/functions/html_output.php on line 322
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Use of undefined constant CSS_BUTTON_POPUPS_IS_ARRAY - assumed 'CSS_BUTTON_POPUPS_IS_ARRAY' in /home/mcas/public_html/includes/functions/html_output.php on line 322
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined property: ot_subtotal::$credit_class in /home/mcas/public_html/includes/classes/order_total.php on line 125
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined property: ot_shipping::$credit_class in /home/mcas/public_html/includes/classes/order_total.php on line 125
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Trying to get property of non-object in /home/mcas/public_html/includes/modules/order_total/ot_coupon.php on line 135
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Trying to get property of non-object in /home/mcas/public_html/includes/modules/order_total/ot_coupon.php on line 135
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined variable: selection in /home/mcas/public_html/includes/modules/order_total/ot_group_pricing.php on line 141
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined property: ot_tax::$credit_class in /home/mcas/public_html/includes/classes/order_total.php on line 125
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined property: ot_loworderfee::$credit_class in /home/mcas/public_html/includes/classes/order_total.php on line 125
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined variable: output_string in /home/mcas/public_html/includes/modules/order_total/ot_gv.php on line 139
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined variable: selection in /home/mcas/public_html/includes/modules/order_total/ot_gv.php on line 201
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined property: ot_total::$credit_class in /home/mcas/public_html/includes/classes/order_total.php on line 125
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined index: checkbox in /home/mcas/public_html/includes/templates/template_default/templates/tpl_checkout_one_default.php on line 95
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Use of undefined constant CSS_BUTTON_POPUPS_IS_ARRAY - assumed 'CSS_BUTTON_POPUPS_IS_ARRAY' in /home/mcas/public_html/includes/functions/html_output.php on line 322
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined index: tax in /home/mcas/public_html/includes/templates/template_default/templates/tpl_modules_checkout_one_shipping.php on line 34
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined index: gps in /home/mcas/public_html/includes/classes/payment.php on line 198
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Trying to get property of non-object in /home/mcas/public_html/includes/classes/payment.php on line 198
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined index: cc_id in /home/mcas/public_html/includes/modules/order_total/ot_coupon.php on line 391
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined index: total in /home/mcas/public_html/includes/modules/order_total/ot_group_pricing.php on line 32
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined index: total in /home/mcas/public_html/includes/modules/order_total/ot_group_pricing.php on line 33
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Use of undefined constant CSS_BUTTON_POPUPS_IS_ARRAY - assumed 'CSS_BUTTON_POPUPS_IS_ARRAY' in /home/mcas/public_html/includes/functions/html_output.php on line 322
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined index: ResCookie in /home/mcas/public_html/includes/templates/frn_black/common/tpl_footer.php on line 65
[09-Jan-2017 10:56:06 America/New_York] PHP Notice:  Undefined index: ResCookie in /home/mcas/public_html/includes/templates/frn_black/common/tpl_footer.php on line 79

From the checkout one log:

2017-01-09 10:44:52 checkout_one: CHECKOUT_ONE_ENTRY, version (1.0.11 (2016-12-29)), Zen Cart version (1.5.5), template (frn_black)
2017-01-09 10:44:52 checkout_one: CHECKOUT_ONE_AFTER_SHIPPING_CALCULATIONS, pass (), free_shipping (), array (
  'id' => 'flat_flat',
  'title' => 'Flat Rate (Best Way)',
  'cost' => '10.00',
)
2017-01-09 10:44:52 checkout_one: CHECKOUT_ONE_SHIPPING_CHECK (flat_flat)
Array
(
    [0] => Array
        (
            [id] => flat
            [module] => Flat Rate
            [methods] => Array
                (
                    [0] => Array
                        (
                            [id] => flat
                            [title] => Best Way
                            [cost] => 10.00
                        )

                )

        )

)

Array
(
    [0] => flat_flat
)

2017-01-09 10:44:52 checkout_one: CHECKOUT_ONE_AFTER_SHIPPING_QUOTES
array (
  'id' => 'flat_flat',
  'title' => 'Flat Rate (Best Way)',
  'cost' => '10.00',
)order Object
(
    [info] => Array
        (
            [order_status] => 1
            [currency] => USD
            [currency_value] => 1.00000000
            [payment_method] => 
            [payment_module_code] => 
            [coupon_code] => 
            [shipping_method] => Flat Rate (Best Way)
            [shipping_module_code] => flat_flat
            [shipping_cost] => 10.00
            [subtotal] => 1
            [shipping_tax] => 0
            [tax] => 0
            [total] => 11
            [tax_groups] => Array
                (
                    [0] => 0
                )

            [comments] => 
            [ip_address] => 107.77.203.150 - 107.77.203.150
        )

    [totals] => Array
        (
        )

    [products] => Array
        (
            [0] => Array
                (
                    [qty] => 1
                    [name] => Aqua-Clo <b></b>
                    [model] => 
                    [tax_groups] => Array
                        (
                            [0] => Sales Tax
                        )

                    [tax_description] => Sales Tax
                    [price] => 1.0000
                    [final_price] => 1
                    [onetime_charges] => 0
                    [weight] => 0
                    [products_priced_by_attribute] => 0
                    [product_is_free] => 0
                    [products_discount_type] => 0
                    [products_discount_type_from] => 0
                    [id] => 40
                    [rowClass] => rowEven
                    [tax] => 0
                )

        )

    [customer] => Array
        (
            [firstname] => Bob
            [lastname] => Hess
            [company] => 
            [street_address] => 2306 greenwood st
            [suburb] => 
            [city] => Lindenwold
            [postcode] => 98002
            [state] => Oregon
            [zone_id] => 41
            [country] => Array
                (
                    [id] => 223
                    [title] => United States
                    [iso_code_2] => US
                    [iso_code_3] => USA
                )

            [format_id] => 2
            [telephone] => 8002939183
            [email_address] => [email protected]
        )

    [delivery] => Array
        (
            [firstname] => Bob
            [lastname] => Hess
            [company] => 
            [street_address] => 2306 greenwood st
            [suburb] => 
            [city] => Lindenwold
            [postcode] => 98002
            [state] => Oregon
            [zone_id] => 41
            [country] => Array
                (
                    [id] => 223
                    [title] => United States
                    [iso_code_2] => US
                    [iso_code_3] => USA
                )

            [country_id] => 223
            [format_id] => 2
        )

    [content_type] => physical
    [email_low_stock] => 
    [products_ordered_attributes] => 
    [products_ordered] => 
    [products_ordered_email] => 
    [attachArray] => 
    [billing] => Array
        (
            [firstname] => Bob
            [lastname] => Hess
            [company] => 
            [street_address] => 2306 greenwood st
            [suburb] => 
            [city] => Lindenwold
            [postcode] => 98002
            [state] => Oregon
            [zone_id] => 41
            [country] => Array
                (
                    [id] => 223
                    [title] => United States
                    [iso_code_2] => US
                    [iso_code_3] => USA
                )

            [country_id] => 223
            [format_id] => 2
        )

    [use_external_tax_handler_only] => 
)
messageStack Object
(
    [messages] => Array
        (
        )

)
Array
(
    [0] => Array
        (
            [id] => flat
            [module] => Flat Rate
            [methods] => Array
                (
                    [0] => Array
                        (
                            [id] => flat
                            [title] => Best Way
                            [cost] => 10.00
                        )

                )

        )

)

2017-01-09 10:44:52 checkout_one: CHECKOUT_ONE_AFTER_ORDER_TOTAL_PROCESSING
order_total Object
(
    [modules] => Array
        (
            [0] => ot_subtotal.php
            [1] => ot_shipping.php
            [2] => ot_coupon.php
            [3] => ot_group_pricing.php
            [4] => ot_tax.php
            [5] => ot_loworderfee.php
            [6] => ot_gv.php
            [7] => ot_total.php
        )

)
order Object
(
    [info] => Array
        (
            [order_status] => 1
            [currency] => USD
            [currency_value] => 1.00000000
            [payment_method] => 
            [payment_module_code] => 
            [coupon_code] => 
            [shipping_method] => Flat Rate (Best Way)
            [shipping_module_code] => flat_flat
            [shipping_cost] => 10.00
            [subtotal] => 1
            [shipping_tax] => 0
            [tax] => 0
            [total] => 11
            [tax_groups] => Array
                (
                    [0] => 0
                )

            [comments] => 
            [ip_address] => 107.77.203.150 - 107.77.203.150
        )

    [totals] => Array
        (
        )

    [products] => Array
        (
            [0] => Array
                (
                    [qty] => 1
                    [name] => Aqua-Clo <b></b>
                    [model] => 
                    [tax_groups] => Array
                        (
                            [0] => Sales Tax
                        )

                    [tax_description] => Sales Tax
                    [price] => 1.0000
                    [final_price] => 1
                    [onetime_charges] => 0
                    [weight] => 0
                    [products_priced_by_attribute] => 0
                    [product_is_free] => 0
                    [products_discount_type] => 0
                    [products_discount_type_from] => 0
                    [id] => 40
                    [rowClass] => rowEven
                    [tax] => 0
                )

        )

    [customer] => Array
        (
            [firstname] => Bob
            [lastname] => Hess
            [company] => 
            [street_address] => 2306 greenwood st
            [suburb] => 
            [city] => Lindenwold
            [postcode] => 98002
            [state] => Oregon
            [zone_id] => 41
            [country] => Array
                (
                    [id] => 223
                    [title] => United States
                    [iso_code_2] => US
                    [iso_code_3] => USA
                )

            [format_id] => 2
            [telephone] => 8002939183
            [email_address] => [email protected]
        )

    [delivery] => Array
        (
            [firstname] => Bob
            [lastname] => Hess
            [company] => 
            [street_address] => 2306 greenwood st
            [suburb] => 
            [city] => Lindenwold
            [postcode] => 98002
            [state] => Oregon
            [zone_id] => 41
            [country] => Array
                (
                    [id] => 223
                    [title] => United States
                    [iso_code_2] => US
                    [iso_code_3] => USA
                )

            [country_id] => 223
            [format_id] => 2
        )

    [content_type] => physical
    [email_low_stock] => 
    [products_ordered_attributes] => 
    [products_ordered] => 
    [products_ordered_email] => 
    [attachArray] => 
    [billing] => Array
        (
            [firstname] => Bob
            [lastname] => Hess
            [company] => 
            [street_address] => 2306 greenwood st
            [suburb] => 
            [city] => Lindenwold
            [postcode] => 98002
            [state] => Oregon
            [zone_id] => 41
            [country] => Array
                (
                    [id] => 223
                    [title] => United States
                    [iso_code_2] => US
                    [iso_code_3] => USA
                )

            [country_id] => 223
            [format_id] => 2
        )

    [use_external_tax_handler_only] => 
)
messageStack Object
(
    [messages] => Array
        (
        )

)

2017-01-09 10:44:52 checkout_one: CHECKOUT_ONE_AFTER_PAYMENT_MODULES_SELECTION
payment Object
(
    [modules] => Array
        (
            [0] => ceon_manual_card.php
            [1] => gps.php
        )

    [selected_module] => 
    [doesCollectsCardDataOnsite] => 
    [paymentClass] => gps Object
        (
            ["code"] => gps
            [title] => Credit Card
            [description] => 
            [enabled] => 1
            [delimiter] => |
            [encapChar] => *
            [_logDir] => /home/mcas/public_html/cache
            [authorize] => 
            [commErrNo] => 0
            [commError] => 
            [reportable_submit_data] => Array
                (
                )

            [gateway_url] => secure.nmi.com
            [sort_order] => 0
            [form_action_url] => https://www.musclechemadvancedsupps.com/index.php?main_page=checkout_process
            [order_status] => 2
        )

)
array (
  'id' => 'flat_flat',
  'title' => 'Flat Rate (Best Way)',
  'cost' => '10.00',
)

... suddenly getting this too - both logs, as described above...

[lat9]

@schoolboy, I've sent you a file to enable the OPC only for me.

@designguy, I've created an account on your store but need the OPC enabled. If you PM me your direct email address, I'll send you a copy of the "enable only for lat9" script, too!

[designguy]

Enabled and pm'ed you.

[designguy]

Actually, I need payments to work in the mean time so when I get the script from you and get it in, then I'll enable it for you.

Thanks for your help!

[designguy]

The owner of the store has asked me to remove the plugin for now, but he has another store that is nearly identical that we may use it on. Basically, the module doesn't seem to be working properly with the payment module as it is a 3-step checkout process API on the gateway side as well as zen-cart. If you need the code for the payment module, I can post it here.

[lat9]

@designguy, what is the payment module name? Perhaps it should be added to the list of confirmation-required payment-methods.

[schoolboy]

@lat9 - I have overwritten the version (1.10) of OPC on the site with 1.12 (githib download) and have not switched it back on as I am not sure if you are "tinkering" as per our PM's .

I'd like to re-activate it while the site is quiet and see if it works. Can I go ahead?

[lat9]

@schoolboy: Don't enable 1.0.12 for the general public on your site. I see the checkout-loop that's introduced in 1.0.12 and I've replicated the issue locally.

I'll report back when I've got a solution.

[lat9]

... and I'm back with that solution. The source of the issue was htmlentities.

@schoolboy's store, which uses GBP as its currency, displays prices like £31.07 but that price value stored in the order is £31.07.

When the OPC's confirmation runs, it checks the current session variables to make sure that the order's overall information hasn't changed from what the customer last saw ... including the order's total value. That current total is copied by javascript (so it's grabbing that displayed price) on the primary OPC page and the processing on the confirmation page is dealing with the htmlentity encoding.

The correction is currently available on the plugin's GitHub repository, as described by this issue and will be part of the forthcoming v1.0.12.

[lat9]

@designguy, what is the payment module name? Perhaps it should be added to the list of confirmation-required payment-methods.

Never mind, found the answer (Gateway Processing Services Module (3-step redirect)) in your previous post. I'm thinking that this payment method might need to be added to the OPC's "confirmation-required" list.

@designguy, would you mind trying the following change? Edit /includes/modules/pages/checkout_one_confirmation/header_php.php, find the following section:

// -----
// There are some payment methods (like eWay) that "replace" the confirmation form via the HTML they return on
// the "process_button" payment-class function.  Rather than hard-code the list in code, below, the following
// constant will be updated as additional payment-methods that make use of that interface are identified.
//
if (!defined ('CHECKOUT_ONE_CONFIRMATION_REQUIRED')) {
    define ('CHECKOUT_ONE_CONFIRMATION_REQUIRED', 'eway_rapid,stripepay');
}

and change that to

// -----
// There are some payment methods (like eWay) that "replace" the confirmation form via the HTML they return on
// the "process_button" payment-class function.  Rather than hard-code the list in code, below, the following
// constant will be updated as additional payment-methods that make use of that interface are identified.
//
if (!defined ('CHECKOUT_ONE_CONFIRMATION_REQUIRED')) {
    define ('CHECKOUT_ONE_CONFIRMATION_REQUIRED', 'eway_rapid,stripepay,gps');
}

That forces the OPC's confirmation page to display for the GPS payment method. Does that correct the issue on your store?