Hello. I am having the same issue as another user, but they flagged their question as solved so I'm making a new one just in case. I can't login properly to YouTube, '''only in Firefox''', even after clearing cache and cookies and disabling add-ons/running safe mode. I can login to my Google account, view my playlists and recommended videos (although the main page with recommendations only shows 5 lines of videos and when scrolling further is not loading). I can't make any edits, '''for example add videos to the "Watch Later" playlist, that require a login. When I click login, Google shows the "405 error "The request method GET is inappropriate for the URL /youtubei/v1/browse/edit_playlist." That’s all we know." or with other URL, depending on the action taken. What can I do? Thank you.'''