In the IPN docs there is this line:
To handle the possibility of transmission and receipt delays or failures, the IPN message service implements a retry mechanism that resends messages at various intervals until you acknowledge that the message has successfully been received.
IPN is sending the same notification 9 times... What do I need to send back? There are no errors in my script. If I use the IPN simulator I get the following message:
IPN sent successfully
It would seem then that the simulator can tell the message is being sent correctly but the real notifier can't?
I am using sandbox if that makes any difference?
Do I need to print anything upon receipt of the notification?