Camera or microphone not working on a call
It is nearly always a permission or a setting, not a broken camera.
What's usually going on
Video call apps need permission to use the camera and microphone, and they need to be pointed at the right ones. A software update, a new headset, or another app holding on to the camera is usually what changed.
Worth trying first
Check the obvious two.
Look for the mute and camera buttons in the call itself, and for a physical shutter or switch covering the camera on your laptop.
Check the permission.
On a Mac: System Settings, Privacy & Security, then Camera and Microphone. On Windows: Settings, Privacy & security, then Camera and Microphone. Make sure the app you're using is switched on.
Choose the right device.
In the app's audio and video settings, pick the camera, microphone, and speaker by name. Computers often switch to a headset or monitor without telling you.
Close other call apps.
Another app may be holding on to the camera. Quit other call apps, then leave the call and rejoin.
Restart.
If it worked yesterday and nothing above helps, restart the computer before the next call rather than during it.
When to hand it over
If it fails again on the next call, or you'd like a camera, microphone, and lighting set up properly so it simply works every time.
Your own technologist, on call.
Tell us a little about your setup. We'll take it from there.