Configure the Apple Server-to-Server Notifications in order for IAPHUB to receive an event when a subscription status change.
Configuring server notifications isn't required but highly recommended, doing so will speed up the sync between Itunes and IAPHUB.
1. Go to the App Store Connect, click on "My Apps" and select your app.
If you do not have an app on App Store Connect, you should create one.
2. Go to App Store > App Information > App Store Server Notifications
3. Copy the server notifications url in the app settings of the IAPHUB dashboard
4. Paste the URL in the "Production Server URL" and "Sandbox Server URL" inputs
You can select the version 2 notifications (the version 1 also works).