Getting the same issue. Can't get even the most basic example working: html !-- example from https://developer.apple.com/documentation/sign_in_with_apple/sign_in_with_apple_js -- script type="text/javascript" src="https://appleid.cdn-apple.com/appleauth/static/jsapi/appleid/1/en_US/appleid.auth.js"/script script type="text/javascript" AppleID.auth.init({ clientId: 'com.myappid', scope: 'name email', redirectURI: 'https://myapp.dev/test/apple/callback' }); const buttonElement = document.getElementById('appleid-signin'); buttonElement.addEventListener('click', function () { AppleID.auth.signIn(); }); /script Created and recreated app IDs and service IDs many times, always results in invalid_client.

Same here. Didn't change anything, it's working now. No response or update from Apple on Feedback Assistant, email or developer forum. Very frustrating.

We've also wasted 1-2 man days trying to debug this issue. We're 90% sure this is a problem on Apple's side. You can verify by testing with a known "good" client_id. For example - when we navigate to this URL: https://appleid.apple.com/auth/authorize?response_type=code&client_id=OUR_APP_ID&scope=email%20name&response_mode=form_post ... which contains our app ID, we get "invalid_client". When we substitute a third-party app ID, such as Uber's: https://appleid.apple.com/auth/authorize?response_type=code&client_id=com.ubercab.UberClient&scope=email%20name&response_mode=form_post ... we get "redirect_uri is required", which is the expected response. We've reached out via Feedback Assistant and Apple's contact form, but no response yet.