Firebase authentication failing with auth/network-request-failed A network error (such as timeout

Question

I have experienced very strange behaviour trying to do Firebase authnetication. Even more, I made a version that works and one that does not. First, the version that works:<

Answer 1

Resolved!

I realized it has something with Content Security Policy, tried various options, and here is the solution. First, instead of inline

onClick="loginToFirebase();"

I had to register event listener

function initApp(){
  document.getElementById('mybutton')
        .addEventListener('click', loginToFirebase);
}

window.onload = function() {
   initApp();
 }

This was not the end of my problems, tried to specify Content Security Policy, but with no result.

After very thoroughly looking at Firebase demo code, I decided to remove <form> tag and that was it!

Hope, it will help someone :)