Videos on Twitter don't play, "The message This browser does not support video playback." appears on the center of a screenshot of the video. Twitter Videos play normally on Chrome. YouTube videos play normally on Firefox. I have the latest version of Firefox and all the plugins are up to date (Java, Flash Player etc). I have experimented changing Hardware Acceleration Where Available box, the media.windows-media-foundation.enabled attribute, clearing the caches, opening in safe mode, nothing makes the videos play. Is there anyone who has had the same problem and managed to solve it. Thank you.