I could use the camera yesterday, but now it's broken...

These are our known solutions to a missing camera:

FAQ: Why does the Camera & Microphone panel not show my webcam's video?

You will probably have turned *every*thing off and on again, I suppose.

Then: Try hitting "set to default camera", up on the right corner of the screen, in the camera window, the burger menu (three little bars) open that menu with those options.

Oh, and is the camera working in other applications? You can always run into hardware issues, of course.