Apple MacBook Air 15-inch camera or microphone is not working in calls

The checks in more detail

Only one app can use the camera at a time, so quit video apps, Photo Booth and browser tabs that hold it. Control Center, Video Effects offers Center Stage, Portrait mode, Studio Light and Reactions; a stuck effect makes the picture look odd, so turn them off. Mic Mode in Control Center selects Standard, Voice Isolation or Wide Spectrum, and Voice Isolation can clip a quiet voice or cut out in noise, so try Standard. If the camera shows a black picture in every app, restart the Mac, and test in Photo Booth.

A camera that is missing from System Information under Camera has a hardware or connection fault, and Apple Support should help. On a work Mac, a management profile can block the camera and microphone for some apps and the Privacy list will not say why; ask the administrator. Keep the lid fully open, because the camera is in the lid and a half-closed lid blocks it. A cover or sticker over the camera blocks it, and a privacy shutter must be removed before video calls. For the microphone, speak toward the screen and keep keyboards and fans away, since the array picks up key clatter.

Updating macOS brings camera fixes. If sound and picture work in one app but not another, contact that app's developer. On a shared or managed Mac, accounts can have different permissions, so the camera may work in one user account and not another; check from the account that is failing. Also check that Screen Time restrictions are not limiting the camera for that account, since a child account can have apps blocked. Switching to the administrator account to compare shows quickly whether permissions are the cause.