Firebase 3x method not working in real device but working on simulator Swift 3.0

Question

We are working with Google Firebase 3.x version and we faced strange issue from Firebase. We are using Swift 3.0 and for getting user details, we are using the following cod

Answer 1

I think the problem is on Authentication. You must have Enable Authentication on Firebase but has not Authenticate user.So you are not allowed to access the database on Firebase.