Something seems to have happened with the Marketplace Account Deletion API. I got an email saying my endpoint was down. It's been fine since last August. I sent the test notification, and it failed. I checked my logs and found that I'm getting the following error message.
"errorId": 2001, "domain": "ACCESS", "category": "REQUEST", "message": "Too many requests.", "longMessage": "The request limit has been reached for the resource."
I revised my code so it would log every incoming request, and what I've found is that when I send the test notification from my developer account, instead of it sending the test notification it's sending dozens of live notifications (over 60 at a time), and is not always sending the test notification which would be identified by having test_user as the username. It seems the issue is with trying to verify the signature.
Edit: I revised my code so it would skip verifying the signature and just send OK. That works, and now I only receive the test notification. However, after changing the code back, it still fails because of the too many requests error. I see the commerce/notification api has a limit of 5000 requests per day. Is it possible there were just that many account deletions in one day, and that caused the issue?