On Windows 10 and 11 set the camera privacy to allow access

You may also need to check your antivirus to see if it is blocking the camera.

1.     Go to Start ► Settings ► Privacy ► Camera
2.     Make sure the "Let apps use your camera hardware" switch is turned on.
3.     Scroll down to "Allow desktop apps to access your camera" and set that switch to on.

On macOS adjust these permissions in System Preferences/Settings

On Sequoia you will be prompted to enable these. On earlier macOS versions they will need to be set manually.

1. Camera
2. Files and Folders
3. Microphone

For example