Hello and welcome to Apple Support Communities GwenAndrea,
We see that your MacBook Air is giving you a message that the camera cannot be found. We know how important it is to be able to have access to the camera on your Mac, and we'd be happy to help.
First, let's have you double check your settings for us. Go to the Apple icon on the top left of your screen, then to About this Mac > System Report > Hardware > Camera. Do you see anything showing there?
If not, try using the articles below to reset the NVRAM and test in safe mode for this issue that you're experiencing.
Reset NVRAM or PRAM on your Mac
How to use safe mode on your Mac
If the issue persists, you'd want to look into having your Mac serviced.
Mac Service and Repair
Thank you for using Apple Support Communities.