I have verified that my sandbox endpoint works for App Store Server Notifications (V2), by requesting a Test Notification.
When I issue a beginRefundRequest in my app for a Sandbox account, my backend does not receive a request. According to the docs this should work in Sandbox too: https://developer.apple.com/documentation/storekit/transaction/testing_refund_requests
What could possible be missing if the TEST notification works, but the REFUND notification doesn't?
Unfortunately without more information it would be difficult to debug. Could you please file a ticket via Feedback Assistant (http://feedbackassistant.apple.com) and we can take a look.
The issue seems to have been resolved on its own without me taking any action. One thing I did notice though is that receiving the notification can have a significant delay, as much as several hours. That wouldn't surprise me in production, but apparently it can happen in Sandbox as well.
