XF 1.5 User upgrade/IPN paypal issue

Please forgive my limited knowledge in the matter but hopefully someone can point me in the right direction.

When our users try to upgrade their accounts paypal isn't linking back to our site properly so their accounts are not automatically upgraded.

The issue appears to be with the Notification url as it doesnt seem to use the one im giving it and just returns with a 404 error.


Thanks in advance.
Thanks for the very quick reply, it looks like you are on the money
i have fixed up the URL and will test shortly

Thanks again!