Firebase Authentication 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.

changing from <form></form> to <div></div> solved this problem:

"A network error (such as timeout, interrupted connection or unreachable host) has occurred in a form element in the HTML. Small bug."

<a (click)="login()" class="nav-link">Login</a>

Do not put href attribute into tag a. It is help to solved my case