Firebase auth works on simulator but not on device (iPhone)

Question

I used Swift 3 and XCode 8.

Here is the error:

2016-12-13 11:28:20.648: Failed to fetch default token Error Domain=NSURLErrorDomain Code=-1001 "The request timed out." UserInfo={NSErrorFailingURLStringKey=https://device-provisioning.googleapis.com/checkin, NSErrorFailingURLKey=https://device-provisioning.googleapis.com/checkin, _kCFStreamErrorDomainKey=4, _kCFStreamErrorCodeKey=-2103, NSLocalizedDescription=The request timed out.

The error happens in code:

FIRAuth.auth()?.signIn(withEmail: self.username!, password: self.password!) { (firUser, error) in...

Any thoughts would be immensely appreciated!