What do you mean by “won’t accept my username or password”? Is it returning “invalid username or password” or does it just refresh the page and ask for the username and password again?
If it is the former, something was typed incorrectly. If it is the latter, it could a few things. Your TV or app that you use updated, and that updated software no longer handles certain protocols or functions. Or, the reverse could be true; the website might have updated something in its login routine that the app can no longer handle.
As Gerald mentioned, the simplest workaround would be to use a casting program available through your phone’s apps store and your TV. Or, you can pipe your computer’s video to your TV via an appropriate media (RGB, VGA, HDMI, etc.)
Hope this helps or at least sheds light on what might be going. Please follow up with any questions or comments.