Why is my IPN failing with HTTP 500 errors?
Your Instant Payment Notification (IPN) is producing 500 (script) errors.
PayPal generates error messages when we don't get an HTTP 200 success response for any reason (including script error 500, SSL handshake validation, network timeout, or server error 503). Either server permission issues or mistakes in your IPN script code may cause these errors.
Debug your IPN script code. You may also need to have your Network or Systems Administrator review your server permissions and logs to determine what's causing the error.
For additional help, see How do I troubleshoot Instant Payment Notification (IPN)?