Are the problem with the people who watch the video, or the people who create, or host the videos?

This bug has now hopefully been fixed, and should work with next release:

https://github.com/LemmyNet/lemmy/issues/3460

It possibly is because there is an error with one of the mod accounts already existing. You could request they remove old admins if they are inactive and this may help to push across the mods. Otherwise, it’s waiting for the next release.

Extra context: https://lemm.ee/comment/1343303

I have same issue on my lemmy.ml acount. It returns a 400 bad request on firefox.

Edit: resolved as of 26/07/23. Can now login.