firebase.com The site cant be reached

we creating a chat app based on firebase, but the problem is that some users can't use the system because their browser can't connect to firebase. Browser clocks google/facebook login and even when this users try to go to firebase.com - they see the same error - The site cant be reached - Err_connection_reset

Some users have two PC - on one they can use/open the firebase.com - on other - they cant, though have same provider.

Using different browsers doesn't help - all have same error. Errors on different browsers:

Error 1 Error 2