Same issue. Using Xcode 12.0.1 - And getting double prompt for login credentials. I am able to use Sandbox test account with iOS 14.0.1. However, iOS 13 and below are returning error - "Cannot connect to iTunes Store".
Noticed that if you get IAP prompt with title "Subscription terms" - It will eventually land into "Cannot connect to iTunes Store" error.
My code uses SwiftyStoreKit wrapper around StoreKit API. I was debugging more into, but it seems to be error within Apple ecosystem.
AppNestDev
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