Built-in camera not working on MacOS Monterey 12.1

My camera is not working on any app (zoom, photo booth, facetime).... The little green light lights up when i open an app that is supposed to use my camera, but nothing appears on the screen, it is just black. A few seconds after I have opened my camera, the light turns off and the screen stays black. Any idea what to do? My software is updated, I have restarted my mac many times but nothing seems to be working. My apps like zoom are also up to date.