I'm creating an authentication workflow for my android app. I'm allowing users to sign in with username/password and various OAuth providers. I'm validating emails and password so that, I know the information I'm passing to Firebase is valid. I'm using
com.google.firebase.FirebaseNetworkException: A network error (such as timeout, interrupted connection or unreachable host) has occurred.
It can also happen when google play services are not running. Try to launch play store and check if it is working. If not reboot of device issue.And also compare the google play services using in the project and google play services in the device are same if not update google play services.
This is just a minor but possible case where it gives the exception.