I think that I have everything configured right, but for some reason I keep coming up with this error.

"This transaction is invalid. Please return to the recipient's website to complete your transaction using their regular checkout flow."

This is the log
Code:
Checking to see if we are in markflow
cart contents: physical

NOTE: $this->showPaymentPage = 0
Customer ID: 1
Session Data: Array
(
    [customers_host_address] => c-68-62-232-217.hsd1.fl.comcast.net
    [cartID] => 
    [cart] => shoppingcart Object
        (
            [observers] => Array
                (
                )

            [contents] => Array
                (
                    [14] => Array
                        (
                            [qty] => 1
                        )

                )

            [total] => 6.99
            [weight] => 0.15
            [cartID] => 
            [content_type] => physical
            [free_shipping_item] => 0
            [free_shipping_weight] => 0
            [free_shipping_price] => 0
        )

    [navigation] => navigationhistory Object
        (
            [observers] => Array
                (
                )

            [path] => Array
                (
                    [0] => Array
                        (
                            [page] => checkout_shipping
                            [mode] => NONSSL
                            [get] => 
                            [post] => Array
                                (
                                )

                        )

                    [1] => Array
                        (
                            [page] => checkout_payment
                            [mode] => NONSSL
                            [get] => 
                            [post] => Array
                                (
                                )

                        )

                    [2] => Array
                        (
                            [page] => checkout_confirmation
                            [mode] => NONSSL
                            [get] => 
                            [post] => Array
                                (
                                )

                        )

                    [3] => Array
                        (
                            [page] => index
                            [mode] => NONSSL
                            [get] => Array
                                (
                                    [type] => ec
                                    [markflow] => 1
                                    [clearSess] => 1
                                    [stage] => final
                                )

                            [post] => Array
                                (
                                )

                        )

                )

            [snapshot] => Array
                (
                )

        )

    [check_valid] => true
    [language] => english
    [languages_id] => 1
    [languages_code] => en
    [currency] => USD
    [updateExpirations] => 1
    [session_counter] => 1
    [customers_ip_address] => 68.62.232.217
    [customer_id] => 1
    [customer_default_address_id] => 1
    [customers_authorization] => 0
    [customer_first_name] => kristy
    [customer_country_id] => 223
    [customer_zone_id] => 18
    [valid_to_checkout] => 1
    [cart_errors] => 
    [sendto] => 1
    [payment] => paypalwpp
    [shipping] => Array
        (
            [id] => flat_flat
            [title] => Flat Rate (Best Way)
            [cost] => 5.99
        )

    [billto] => 1
    [cot_gv] => 0
    [comments] => 
)
I would GREATLY appreciate any help. :)

Thanks!
Kristy