apple login (using AppleAuthentication) question about documentation + error code 1000

In the AppleAuthentication documentation, under Configuration it says:

  1. Next, go to the “Keys” page and register a new key. Add the “Sign In with Apple” capability, and make sure to choose the correct primary app on the configuration screen.

So my first question is: what do I do with this key. I saw nowhere that mentions this key…

And my main issue is that I’m getting an “1000” error code from apple login. I though maybe the key above has something to do with it.

My code: (frontend, Expo)

    const appleSignInHandler = async () => {
        Alert.alert('got here--appleSignInHandler'); // ! this alert works
        try {
                 const credentials = await AppleAuthentication.signInAsync({
                    requestedScopes: [
                        AppleAuthentication.AppleAuthenticationScope.FULL_NAME,
                        AppleAuthentication.AppleAuthenticationScope.EMAIL,
                    ],
                });
                Alert.alert('credentials are', String(credentials))
                // signed in
        } catch (e) {
            Alert.alert('POST apple-login error: ' + e); //! this alert works with the 1000 error code
        }
    }

This is a kind old question, But I have being strugling to solve a “Sign up not completed” (“Inscrição não concluída” in portuguese), and revoking such key solved my problem. I’m not so sure we should create this key, at least now in Feb 2022.