I have signed out from the store in device settings. I entered user credentials only in my App. I have set up a brand new (actually around 4 times) test user.
Why this message keep poppin' up?
Is it something connected to iOS 5, automatic app sync, or iCloud?
I had exactly same problem with sandbox in-app purchases, in built-in model (no receipt verification), app received valid products, now i called addPayment, everything alright. But now "Verification required" appeared and payment was canceled.
After hours of pain I discovered, my problem was in test account.. i created test account for Czech Republic iTunes store... and that was the reason of fail. Dumb. I tried to create Canadian test user and it suddenly worked! "Verification required" will no longer appeared.