EDIT: Question retracted. The answer was to "turn it off and back on again" (i.e. close and restart firefox). Site works fine now with all addons and tracking protections enabled. messages.google.com isn't working for me anymore. This is with Firefox 80.0.1 (64-bit) on Windows. All I get is a blank page. The network monitor indicates a bunch of things are "Blocked", but I don't see where it explains why they were blocked. I've disabled all addons, set tracking protections to standard, and disabled Enhanced Tracking Protection for messages.google.com. Am I missing something?