[Solved] MySubscriptions 1.7.2 error

[Tester0]

It's the second time already which user isn't moved to the group for which he paid after succesfully completing the payment.
I've been told that they're taken back to the mysubscriptions page.

IPN should be configured correctly with the url:
http://****.info/mysubscriptions_paypal.php

what can be wrong?

EDIT: I keep getting messages from users which aren't moved to the new usergroup after purchase...