Same signature here. Team 9MZTYK3NV9, bundle com.myboxmp.donopalier (App ID registered 2026-08-22, Sign in with Apple enabled 2026-08-25). Native sheet shows "Sign Up Not Completed", the app receives ASAuthorizationError.canceled (1001), no credential is issued, backend is never reached. Reproduced on two iPhones with two independent Apple Accounts that had never signed in to this app; both accounts work with Sign in with Apple in other teams' apps on the same devices. Verified: entitlement present in both the profile and the signed binary (read from the distributed IPA), PRIMARY_APP_CONSENT via the API, single ACTIVE profile, agreements accepted, four TestFlight builds fail identically with no code changes. Filed FB24538045. Requesting the same server-side check that resolved GW7XA5CX69 and FRL3DTJQ62.