Hello Didier,
Thank you for posting question on Microsoft Windows Forum.
Based on the issue description. As this is affecting both Chrome and Edge (which share the same "Chromium" engine) but not Firefox, the issue is likely how that specific engine is interacting with your Windows Display Manager, or the window is technically open but positioned off-screen where you can not see it.
I would like to share some suggestions with you to see if it works.
1.Check the Possibility of "Off-Screen".
- Hover over the Chrome/Edge icon in the taskbar so the little preview pane pops up. Right-click on that preview pane (not the icon itself). If you see Move, click it. Note: If "Move" is greyed out, click "Restore" first, then try again. Do not move your mouse. Immediately press one of the Arrow Keys on your keyboard (Left or Right) once. Now, move your Mouse around. The browser window should theoretically be "stuck" to your mouse cursor. Move it to the center of your screen and click to drop it.
2.Check The Possibility of Ghost Monitor.
- Right-click your Desktop and select Display Settings. Look at the diagram of screens. Do you see a square labeled "2" or "3" that shouldn't be there? If you do, select it and scroll down to "Multiple displays" and choose "Disconnect this display" or ensure your main screen is set to "Make this my main display."
3.Try a Portable or Canary Build for Workaround or Test.
- Download Chrome Canary or Edge Canary (different install path) or Chrome Portable and try running. If those open, the issue is likely profile/settings related rather than core OS.
Hope the above information is helpful!