Having another go at installing this version. I notice this warning was in an earlier post but as it wasn't the main issue it never got addressed.

PHP Code:
[06-Sep-2022 16:00:53 Europe/LondonRequest URI: /...../admin/index.php?cmd=orders&page=1&oID=31216&action=editIP addressxxx.xxx.xxx.xxx
#1 square_webPay->__construct() called at [/admin/orders.php:521]
#2 require(/admin/orders.php) called at [/admin/index.php:11]
--> PHP Warning: Use of undefined constant MODULE_PAYMENT_SQ_WEBPAY_TESTING_MODE assumed 'MODULE_PAYMENT_SQ_WEBPAY_TESTING_MODE' (this will throw an Error in a future version of PHPin /includes/modules/payment/square_webPay.php on line 106.

[06-Sep-2022 16:00:53 Europe/LondonRequest URI: /..../admin/index.php?cmd=orders&page=1&oID=31216&action=editIP addressxxx.xxx.xxx.xxx
#1 square_webPay->__construct() called at [/admin/orders.php:521]
#2 require(/admin/orders.php) called at [/admin/index.php:11]
--> PHP Warning: Use of undefined constant MODULE_PAYMENT_SQ_WEBPAY_ACCESS_TOKEN assumed 'MODULE_PAYMENT_SQ_WEBPAY_ACCESS_TOKEN' (this will throw an Error in a future version of PHPin /includes/modules/payment/square_webPay.php on line 111. 
I can add quotes to the code to get rid of the warning but I'm not convinced this is the solution as nobody else seems to have the issue.

I am using V1.0.1 from the downloads on Zen V1.5.7d and PHP 7.4

Any pointers please?