this is a great plugin that unfortunately fails to work on my server. Here is the problem.
I have installed paypal framework and configured it. While testing the plug-in with sandbox, paypal framework sends transaction details to sandbox (I can see that from Paypal Sandbox website), but the listener does not receive the IPN message from sandbox or fails in checking if the IPN was correct (validation). Regardless I do not receive any messages and no actions are performed.
Two possible reasons:
1. Paypal framework is not configured based on the latest specs from Paypal (https://www.x.com/content/bulletin-ipn-and-pdt-scripts-and-http-1-1).
2. Plesk blocks the IPN (http://kb.parallels.com/en/112756).
But I do not know how to deal with these..