Mozilla has been tracking and working on a known Twitter issue for 20 days. Firefox users might see blank pages or errors when trying to visit the social network’s website. Mozilla has not shared the Firefox versions affected by this problem. Users say the issue has started to appear on both mobile and desktop devices after updating to Firefox 81.0 last month. Hard reloading Twitter’s site using CTRL+F5 will also temporarily allow you to open Twitter pages temporarily. Users can also get rid of the errors by disabling dom.serviceWorkers.enabled.
Source: https://www.bleepingcomputer.com/news/technology/mozilla-shares-fix-for-twitter-not-working-on-firefox/