We are implementing an auto-renewable subscription in our app.
Currently, we have checked cancellation_date_ms has a date value inside of receipts when upgrade subscription in same group.
And also received Server to Server Notifications 'Cancel' notification.
But sometimes when we doing upgrade the subscription, cancellation_date_ms does not have values and not receiving Server Notifications.
In our app, it's vital to stop service when users upgrade the subscription.
We want to know all cases cancelling user's subscription when they have upgrade their auto-renewable subscription.
If it is vital to know the subscription status then take a receipt and send it the Apple servers to get latest_receipt_info each time the user opens the app. You cannot rely on getting any particular notification and you can rely on the receipt sent to you from Apple servers.