Open the Camera app in Windows and check if the webcam is working in that app.
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If the webcam is working in that app:
Open the Settings App.
Go to Privacy and Security - Camera.
Ensure permissions to use the webcam is enabled and also ensure those two apps are enabled to access your webcam.
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If the webcam is not working in the Camera app:
Look at the function keys (F1 - F12) on your keyboard, if one of them has a camera icon, press that key or Fn + that key to unlock the webcam.
If that was not the problem, look at the camera lens above your screen, is there a small privacy slider that needs to be opened to access the webcam?
If the webcam is still not working, right click your Start Button and open Device Manager.
Expand the 'Cameras' section.
Please provide a screenshot of that full Device Manager window.