I use MemberPress plugin to sell courses via Paypal Standard. It uses IPN for creating transactions, pause/resume and cancel subscription.
It works perfectly fine when I use my Sandbox account credentials. But it isn't working in case of Live paypal account. In Paypal IPN history it says, Paypal is getting 500 error from the website.
I have talked with both Paypal and MemberPress. Paypal says that the server doesn't respond to the notifications. On the otherhad MemberPress says that it's not getting notifications.
I cannot figure out what is wrong. And the most confusing thing is 'it works perfectly with sandbox account'.
I highly aappreciate any help or ideas. Thanks!
By the way, I was able to fix the issue... There was an anti spam plugin which was blocking live Paypal but wasn't blocking Sandbox Paypal.