Hi Edward, are you getting a flash of a window or Taskbar button, then it disappears? There was recently an issue with Microsoft Family Safety blocking all browsers other than Edge. To test whether this is the issue, you can try this little hack: Using Windows File Explorer, open C:\Program Files\Mozilla Firefox\ Right-click firefox.exe and click the little rename button at the top of the context menu. Add 1 to the file name so it looks like this: firefox'''1'''.exe and press Enter to save the change. Then try launching it by double-clicking firefox1.exe. If Firefox starts normally, most likely it is the either Microsoft Family Safety or another security program killing Firefox. (In the bad old days before people had basic security software, malware also would kill modern browsers, but I don't know whether that still happens.)