title: The provided registration token is not registered
body: <p>I'm trying to send push notification for iOS via Google cloud functions but it returns error that <code>The provided registration token is not registered</code>. But I've checked it by debugging my app and the FCM registration token is correct. After that I've tried to send push notification via Firebase console to single device by providing FCM token but it failed due to <code>Unregistered registration token</code>. How this happens because there is no issue with device FCM token?</p>