Thanks for the reply, Doc, and my apologies for the incorrect posting. - I was trying to keep like subjects together.

Anyway, despite the successful returns from the tests, I am receiving emails from PayPal telling me:

Please check your server that handles PayPal Instant Payment Notifications (IPN). Instant Payment Notifications sent to the following URL(s) are failing:


https://mysite.tld/ipn_main_handler.php
I have verified that the file is present, have replaced it with a copy of the file from my original files, and have also tried

http://mysite.tld/ipn_main_handler.php

with no success.

The settings in PayPal have been checked several times, as have my settings in admin for the PayPal Express module, so I'm at a complete loss as to what is causing this.

I have even been through my files replacing files with originals where the existing files had been overwritten by contribution files and have also tried removing and reinstalling the PayPal module.