WordPress Membership Plugin
i disabled all the plugin and the theme and nothing is shown in the logs of your plugin,
I used the ipn simulator directely or the sandbox paypment with fake users using the payment button built with your tool?
these the ipn simulator options:
eCheck – pending
eCheck – complete
eCheck – declined
Express Checkout
Cart checkout
Web Accept
Refund
eBay checkout
Reversal
Canceled Reversal
tnx
Yes a subscription button made with your plugin as described here
https://simple-membership-plugin.com/create-paypal-subscription-button-inside-the-simple-membership-plugin/
and followed the ipn configuration you linked.
i checked the server logs and paypal is sending the ipn notification but the plugin is not reading the data i suppose