Important
Apple only returns the user object the first time the user authorizes the app. Persist this information from your app; subsequent authorization requests won’t contain the user object.
(https://developer.apple.com/documentation/sign_in_with_apple/sign_in_with_apple_js/configuring_your_webpage_for_sign_in_with_apple)
So you should go to Settings->ID Apple ->Password&Security and remove the app from apps that use your Apple ID
Now you can register again and apple will send the userInfo.