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
        }
    }