Update (July 31, 2026): We ran a clean cross-team control experiment with Apple's unmodified official Juice sample. On the same physical iPhone 12 Pro (iOS 26.3.1), with the same Apple ID and Face ID: Team FNDQRVAXU4, App ID com.vybers.placeholder.vybersworld.fndqrvaxu4, signed with an Apple Development profile containing com.apple.developer.applesignin = Default: Sign in with Apple succeeded and Juice received ASAuthorizationAppleIDCredential. Team 42U93YD944: our app and an official Juice build signed for that team both failed after Face ID. The sheet said registration could not be completed; no credential or identityToken was returned. The device log included AKAuthenticationServerError Code=-24000. The successful app was installed directly on the same phone. Its signed entitlements were verified for the matching application-identifier/team-identifier and com.apple.developer.applesignin = Default. This isolates the problem to a likely team-scoped Sign in with Apple/AuthKit backend registration or synchronization issue in 42U93YD944, rather than the Apple ID, device, Face ID, client code, signing capability, or token verification. Please compare the backend state for 42U93YD944 and FNDQRVAXU4 and resynchronize if needed. Logs and signing details are available under support case 20000123689964.