I'm experiencing the same happening, partial blank page after payment on order details page, but I'm getting this in the logs:

PHP Warning: require(/includes/modules/payment/square_support/square_admin_notification.php): failed to open stream: No such file or directory in /includes/modules/payment/square_webPay.php on line 505.

[31-May-2022 17:01:24 America/Detroit] PHP Fatal error: require(): Failed opening required '/includes/modules/payment/square_support/square_admin_notification.php' (include_path='.:/opt/cpanel/ea-php74/root/usr/share/pear') in /includes/modules/payment/square_webPay.php on line 505

I ran the update above (post #131) but error log continues (updated to webPay over the weekend).

Doing a search I found includes/modules/payment/square_webPay.php has this line of code in it require(DIR_FS_CATALOG . DIR_WS_MODULES . 'payment/square_support/square_admin_notification.php');

Checking the square_webPay folder doesn't contain anything remotely similar to this file in it. Should I modify the file by deleting the line/commenting it or is there another line that should replace it?