Apple warns customers to avoid closing their MacBook, MacBook Air, or MacBook Pro devices if they use a camera cover thicker than 0.1mm to avoid display damage. Apple says that Mac cameras are engineered to not activate if the camera indicator light doesn’t also turn on to protect the users’ privacy. Users must first give permission to apps that want to use the FaceTime HD camera to control access to your Mac’s camera (you can go here to learn how to use it in System Preferences)
Source: https://www.bleepingcomputer.com/news/apple/apple-closing-macbooks-with-camera-covers-leads-to-display-damage/