S2Member API/Notifications for Payment Not Being Sent

Hi,

I have a Wordpress site with S2Member integration. I put a Paypal button to accept payments, and I am testing if I can get notifications whenever I receive payments, and I am no.

I added a server to check if API/Notifications are sent, and here is what I found:

  1. Registration Notifications are being sent, because logs show that I receive events
  2. Payment Notifications are NOT being sent, because logs on the server are silent.

What could be wrong?