In our app we are using server side verification of receipts with app store. However the backend seems to always get 21002 error code from apple after verifying the receipt.
We are testing our IAP with TestFlight and we are able to successfully buy an IAP on TestFlight. The IAP is approved in AppStoreConnect but we need the Cleared for Sale checkmark not checked (so that it is not available for purchase in App Settings). Is is possible that this is the reason apple is unable to verify the receipt even for purchases in TestFlight. Or such purchases should be ok and we should look for the problem elsewhere?