I'm sorry Chuck,
yes the process of the payment works very well BUT nothing appears in payment_verification.php !!!
Well I propose you log as a test at GD Annonces - Index principal
login : lololo password : 123456
then in subscription list, you take one and then cancel clicking "annuler et retourner sur GD Concept" and you'll see all is white in payment_verification.php
I verified the file, all you told to write is already written !!!!!
it's a big problem for us !