Paypal IPN issues

We’ve used smartforms & smart donations for about 6 years now and absolutely LOVE the functions and simplicity. We’ve just recently run into an issue where some items aren’t working properly and we find ourselves in need of help.

We have basic info forms online, those are working just fine. We have several donation buttons thru smartdonations and those are working fine. Where we’re running into issues is with the forms that take payments/donations, either thru smartforms or smart donations. These act fine on the customer side, and take them to paypal to process their donation/payment with no issue. But the URL for paypal IPN’s seems to be invalid, so it doesn’t actually process the customer form. The form information isn’t emailed and doesn’t even show up in the database (I’m guessing because it doesn’t see it as a completed form since the IPN didn’t verify?).

We’ve tried resetting the IPN, having paypal remove the IPN url that was the issue to reset it.. all to no avail. Paypal is saying it’s an in app issue. Any help or guidance would be welcome – we don’t want to make our donors unhappy by having to request info (sometimes lengthy) multiple times.

The URL that’s failing ends in /wp-content/plugins/smart-donations/ipn/rednao_paypal_ipn.php in case that’s informative.

The page I need help with: [log in to see the link]