We are testing version 1.0 Build 29 through TestFlight after a Guideline 2.1(b) rejection: Purchase did not respond on iPad Air 11-inch (M3). Paid Apps Agreement is Active, and subscription price, availability, localization and review screenshot are present. Restores worked, but a fresh purchase is not yet verified. On iPhone 13, Build 29 is installed, Developer Mode is on, and Media & Purchases was signed out. The tester reports signing into Developer > Sandbox Apple Account, then trying to sign into the app. During this sequence an email verification prompt was followed by: "iTunes account creation not allowed. This Apple account cannot be used with iTunes Store at this time. Please try again later." The app uses Sign in with Apple separately from StoreKit. We have not isolated which system authentication flow produced the error. What is the supported sequence for regular iCloud/Sign in with Apple alongside a Sandbox Apple Account for TestFlight purchases? Which diagnostics distinguish account setup failure from app authentication or StoreKit failure? Should we escalate through Feedback Assistant or Developer Support, and which logs should accompany the report? We want to verify a fresh purchase on an 11-inch iPad before resubmission.