Environment App: Web app (Sign in with Apple JS / redirect flow) Hosted over HTTPS (valid TLS cert via AWS ALB) Tested on latest Chrome, Safari, and Firefox Reproducible in normal + incognito/private windows Expected behavior When clicking "Sign in with Apple", the popup should render the Apple login form and then redirect to our configured callback endpoint Actual behavior Apple Sign-In popup opens successfully Page loads only the Apple header shell: • Apple logo • "Apple Account" • Collapsed "Sign in" section The actual login form (email/password entry) never renders No visible error shown to the user No requests ever reach our backend callback endpoint Configuration status Services ID created and enabled for Sign in with Apple Domain verified and added to Services ID: Return URL configured exactly: Primary App ID has Sign in with Apple capability enabled Key created and associated with the App ID CSP allows What we have already tried Re-saving Services ID configuration multiple times Regenerating Key and re-binding to App ID Verifying client_id matches Services ID identifier exactly Waiting >24 hours for propagation Testing across multiple browsers and devices Key observation The flow appears to stop before authentication UI renders fully, and no redirect/callback is ever triggered, suggesting the issue occurs within Apple’s authorization session before completion. Question Is there any known requirement or verification step for Services IDs using a domain-style identifier, or any additional Apple-side configuration/activation step that could prevent the login form from rendering even though the initial authorize page loads?