Same issue here, Submitted via Feedback Assistant: FB24297924 — it includes the Bundle ID (ai.fishnerd.app), Team ID (69FG2M5B5T), the affected Apple ID, the reproduction timestamp, and a sysdiagnose captured on the affected iPhone with the Accounts/AuthKit logging profile installed, immediately after reproducing. Same signature as this thread: the native account-creation sheet completes normally (name + Share/Hide My Email steps) and then shows "Sign Up Not Completed"; the authorization callback returns ASAuthorizationError.canceled (1001) with an empty userInfo even though the user did not cancel, and the flow fails before any identity token is issued, so none is included. The same Apple ID signs in to other third-party apps without issue, and this is a recently created App ID — matching the pattern reported here. Happy to provide a screen recording or anything else needed. — Marcelo (FishNerd)