It worked for me after reloading and turning off uBlock. Maybe you also need to reload a few times.
From my little testing it seems like uBlock doesn't make a difference (shows 0 blocked elements) and it's really the reloading that does the trick. It seems to switch between working and not working every few seconds.
Edit: I just tested a bit more and last time the non-working period was a good minute. I'll stop DoSing now.
Probably one of your extensions blocking it. Turn off stuff like ublock and privacy badger and reload. I tried on Mac Firefox and it does indeed fail in even safe mode.