Yesterday the paypal IPN listener suddenly stopped receiving messages from paypal. The listener was unchanged, and IPN is still turned on in the paypal settings. In the history, it shows a few messages. The messages Have no HTTP response code. My logs on cPanel don't seem to show any connection to the IPN listener. If it matters, my listener runs over plain http.
Is there any way I can debug this? The only data I seem to have is that paypal just isn't sending the IPNs, but it claims to be trying.
EDIT: The very first thing in my php listener is to set the header to 200 OK.
I'm not allowed to comment at this point in my Stack Overflow career, but I fought with my listener a lot this past month (successfully) so we'll see if I can help.
First, how long was your listener working for prior? Was it just in the sandbox or was it live for a while?
If your IPN history says thats it is trying to reach your listener and can't, I would head back to paypals IPN simulator and confirm that the handshake still occurs. If not, there could be something wrong with either the verification code that interacts with paypal, or I have also noticed that if an error occurs on your backend code that the IPN may reject it as well. If all of that fails, the IPN simulator is successful, and the history still says it's trying, it may be good to see the guts of your listener posted.