Yep, I've got this one figured, I think. It's a 'website disconnected penalty' thing - IMDB stopped you viewing their trailers if you blocked ads, Vimeo blocks vids if you block autoplay and ...just by elimination * from the things you've tried......Twitter is stopping you viewing their vids if you block their....cookies!billku wrote:Ugh, I know, it's a hard one, so weird.
Go to a Twitter page, right click, select Page Info > Permissions > Cookies and select 'Allow for Session'. After a page reload or maybe a Firefox restart, the vids should play.
* normal/safemode/new profile/ renamed prefs.js on normal and figuring the differences each makes.
This 'solution' will either be really good or totally wrong.