Need Help Debugging Unity IAP for IOS Devices

My mobile app and all the consumables have already been approved by the Apple review team. I am now trying set up some in-app purchases through Unity IAP for iOS devices. Registering the various product IDs, the initialization process seems to have passed successfully. However, when I tried to make a purchase using an iPad connected to a Mac, I received an error message on XCode saying: UnityIAP: No App Receipt found The purchase failed. The reason given for the error was: OnPurchaseFailed: FAIL. Product: '2gold', PurchaseFailureReason: Unknown On the Unity editor, the dummy purchase did go through without any problem. So what could be the reason? What is an App Receipt? How should I go about pinpointing the source of the problem? Must I first test the IAP in a sandbox environment? Attached is the relevant script. If necessary, we can communicate through TeamViewer.