We need our server to receive notifications about changes in subscription statuses. To achieve this we followed the instructions from https://help.apple.com/itunes-connect/developer/#/dev0067a330b.
Our server supports App Transport Security (ATS) protocol. It was tested with this service https://apptransport.info/. So all requirements seem to be fulfilled.
We entered the target URL into the “Subscription Status URL” field. But we haven’t received a request (GET, POST, PUT) to the specified address after starting and expiring subscriptions in our sandbox.
Is there any way to troubleshoot this kind of problem?