Our case supports your registration-date finding from the other direction: our entire team is new (enrolled 2026-07-13, capability first enabled 2026-07-16), so we have no pre-2026 App ID to fall back on — and every App ID of the team fails identically with "Sign Up Not Completed" / ASAuthorizationError 1001, including a clean-room probe App ID created specifically to test this. If the failure is scoped to recently-registered App IDs not propagating into the identity service, a brand-new team fails everywhere, which is exactly what we see. Ruled out: entitlement (verified in the embedded provisioning profile), agreements (Active), scopes (unset and .fullName), signing (Xcode and TestFlight both fail), device/Apple ID (3 devices, 2 independent Apple IDs; third-party SIWA sign-ups work fine for the same Apple IDs). akd log with the Accounts profile shows the GSA sign-up SRP returning 200 with M2 missing (bad password) and null account fields — the identity server aborting the sign-up ceremony server-side. Filed as FB23826495, referencing yours (FB23726069) and FB23716661. Precedents suggest Apple fixes this class server-side: thread 790827 (official, June 2025, 5 days) and thread 790323 (same M2 signature, 11 days).

Same issue, same signature, independent team — adding as a data point that this is an active server-side recurrence. Team Z4ZFKAR4DZ (enrolled 2026-07-13, Sign in with Apple capability first enabled 2026-07-16): every client of the team fails first-time sign-up with "Sign Up Not Completed" → ASAuthorizationError 1001 with empty userInfo. Reproduced across 3 devices, 2 independent Apple IDs, 2 App IDs (production app + a clean-room probe created just to test this), scoped and scope-less requests, Xcode and TestFlight signing. Entitlement verified inside the embedded provisioning profile; agreements Active; a first-time SIWA sign-up into a third-party app succeeds on the same device/Apple ID during the failure window. One detail that may help triage: with the Accounts logging profile installed, akd shows the GSA sign-up SRP exchange returning HTTP 200 with the server proof missing — AppleIDAuthSupport: setError: 2:M2 missing (bad password), account fields all null — then akd -7003. Same signature as thread 790323 (June 2025, self-resolved after 11 days) and consistent with the officially acknowledged June 18–23 2025 incident (thread 790827). Filed as FB23826495 with sysdiagnose, screen recording, and the akd capture.