Membership does not upgrade user account

We have your older Membership 1 plugin.
(The most powerful, easy to use and flexible membership plugin for WordPress, Multisite and BuddyPress sites available. Offer downloads, posts, pages, forums and more to paid members. Version 3.5.2.9 | By WPMU DEV | Visit plugin site)

Our problem:
The membership plugin is not be getting the proper confirmation back from PayPal that the payment went through and therefore is not upgrading the membership level from free to PRO (premium memberships) Please help!?!?! =)

We do not want the new version, we tryed this last year when you released it and it was a huge mess. Please can we just update the one we have. If WP DEV can fix this we will definitely reconsider to keep using our existing developers. We really hope you can help us with this issue.

Chad