Open the Camera app in Windows, is the webcam working in that app?
1
If the webcam is not working in the Camera app:
A
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.
B
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?
2
If the webcam is working in the Camera app, open the Settings App.
Go to Privacy and Security - Camera
Ensure all apps are allowed to access your webcam in there.