Hi, @Izzy Celé
The 0xA00F4244 error means Windows can't see any camera at all, so the Camera app has nothing to open. Since the driver and privacy steps didn't help, the camera may be turned off somewhere else in Windows, or another program may be blocking it.
Here are some suggestions you can try:
Open Settings > Bluetooth & devices > Cameras. If your camera shows up in the list of disabled cameras, click Enable next to it. This setting is separate from Device Manager, so it's easy to miss.
Run the built-in camera troubleshooter. Open the Get Help app, type "camera" and follow the steps. It resets the camera services and checks whether the camera is missing or disabled.
In Device Manager, click View > Show hidden devices. Then expand Universal Serial Bus controllers and look for a grayed-out camera or an Unknown device. If you find one, right-click it, choose Uninstall device, and restart.
Repair the Camera app. Go to Settings > Apps > Installed apps, find Camera, click the three dots and choose Advanced options > Repair. If that doesn't work, click Reset.
Some antivirus programs and manufacturer tools have a "webcam protection" or "camera privacy" option that can block the camera, so check whether it's turned on and turn it off. Lenovo Vantage is one example.
Do a full shutdown. Hold Shift while you click Shut down, wait about 30 seconds, then turn the PC back on. Unlike a normal shutdown, this fully resets your hardware, so Windows has to detect the camera again.
If none of these work, let me know your PC model and whether the camera is built in or plugged in by USB.