I'm sorry to hear that you're experiencing this issue. I'm happy to help.
What is the make and model of your device?
Press Windows + R, then type MSINFO32 and hit ok.
Take a screenshot of that window and attach it to your next reply.
Some laptops have a physical switch to enable the camera:
Method 1: Locate a button on your keyboard featuring a camera symbol, typically on the F1-F12 keys.
Similar to this:
https://th.bing.com/th/id/OIP.JDIWtfGA4gfWgwhPERI9ZAHaE5?pid=ImgDet&rs=1
Press that key or Fn + the camera logo key to enable the camera and then you can use it again.
Method 2: Please check the camera lens carefully to see if there’s a cover, such as a camera shutter. Slide it to uncover the webcam.
Method 3: Press the Windows key + X, and choose Device Manager.
Expand Cameras or Imaging Devices
Right-click your camera, and select Uninstall Device.
Ensure to tick "Delete driver software for this device" when prompted.
Restart your PC
Check if the issue is resolved.