There was a known temporary issue on Firefox that caused a blank or error page when loading Twitter on older versions of Firefox. This issue has been fixed on release 81.0.2.
Please update to verson 81.0.2 or above to fix this issue. See Update Firefox to the latest release to learn more.
If you're unable to update to a more recent version, please try the following temporary workaround:
- Enter about:serviceworkers in the address bar.
- Look for Twitter on the list then click its button.
- Twitter should load the next time you visit it.