I have an app with in-app subscription purchase. Consider the user tries to buy a subscription, but my verification server is down and I cannot validate the receipt, so I notifyFulfillment with UNAVAILABLE because I cannot deliver the purchased content.
Q1: Is it ok to notify with UNAVAILABLE in this case, or should I be doing something else?
Q2: If that is ok to do, will the user be charged when I notifyFulfillment with UNAVAILABLE?
Q3:When testing with sandbox, after notifying with UNAVAILABLE, if I try to purchase the subscription again, I am told I am already subscribed. Is that normal behaviour? Personally, I would expect for the user to be allowed to retry the purchase since it failed last time.
Q4: If my assumptions are wrong, what is supposed to happen if we fail to verify the purchase and cannot deliver the content?