Windows 11 Pro - Dell XPS8940 desktop - i9 Firefox will not play video from a website. If I save the video, it is a MP4 file. Windows Media Player and VLC will play the video file. But the browser shows the message: "No video with supported format and MIME type found." Chrome and Edge will play this video correctly in their browsers. Firefox will not play the video on 3 different computers, and even when a different user account is involved (without Firefox sync). The evidence seems to point at firefox. The website is a Wordpress site. Is it possible that the website is the problem? If so, why do Edge and Chrome work? I uninstalled Firefox (latest version) and reinstalled it. Not fixed. My windows updates are current, as are Dell updates. This is stumping me. I hope someone can help.