Apple MacBook Pro 16-inch camera or microphone is not working in calls

The checks in more detail

Open System Settings, Privacy and Security, Camera and Microphone, and make sure the app you are using is listed and switched on. A newly installed app, or one updated after a macOS update, may need permission again, and the app must be restarted to use it. Only one app can use the camera at a time on many setups, so quit other apps that might hold it, such as another call app, Photo Booth, a browser tab with a video call or a screen recorder.

In the call app itself, open the settings and choose the built-in camera and microphone, since an external device or a virtual camera, such as a streaming tool, may be selected, and the app may have picked a display's camera or an iPhone through Continuity Camera. Check Control Center for video effects and microphone modes, such as Voice Isolation, Wide Spectrum and Standard, and Portrait or Center Stage, which can make the picture odd; in the microphone mode menu choose Standard to test. If the camera is still black, restart the Mac, update macOS in System Settings, General, Software Update, and test in Photo Booth to see whether the problem is the app.

A screen protector, a camera cover that is too thick or a closed lid on an external display setup can block the camera, and a clamshell setup uses the external display's camera. For the microphone, check Settings, Sound, Input and the level meter while speaking; the three microphones are placed above the keyboard, so keep them clear and avoid typing near them. Apple Diagnostics, by holding the power button at start-up, tests hardware. If the camera or microphone fails in every app after a restart, contact Apple Support with the serial number.