Since a lots of people failed to load the twitch stream,i experienced that too…So, today im gonna help you guys to solve this problem…actually you just need to click on the video quality which is just become invisible and beside your “report problem” button…while the stream is loading you just need to click left side of the 'report problem"button then you can choose the video quality…after u chose the video quality,the stream will load successfully…the stream will not load if you choose the video quality after it failed to load…Do it before the video failed to load… Hope this can help all of you…have a nice day 
twitch failed to load video …
how to fix ? but only firefox can use