If you go to login page and you have saved login/password for that page the browser will get fields filled already.
BUT the sign in button is DISABLED until you write something in either input field.
Sign in button must not be disabled.
Was just about to open an issue about this. In my case I use a password manager to fill in username/password. My current solution is to delete the last character in my username, type it back and then the button detect the input.
This issue hasn't had any updates in a while. If this is still a problem, please create a new issue.
This is still an issue.