my camera is not woking on MacBook Air. Not on Photo Booth or FaceTime.

Hello Lin8160,

Welcome to Apple Support Communities!

If we understand your post correctly, the camera on your Mac isn't working for Photo Booth or FaceTime. We're here to help!

The article that you came from, If your built-in camera isn’t working on your Mac, is a great resource for the built-in camera not working.

"Check the camera indicator light

If the camera indicator light next to the camera flashes green on your Mac notebook, contact Apple.

Update your software

Make sure your software is up to date.

Check Screen Time settings

If your Mac is using macOS Catalina and you use Screen Time, make sure your camera is turned on and apps that use the camera have time available.

1. Choose Apple menu  > System Preferences, then click Screen Time.
2. Click Content & Privacy in the sidebar, then click Apps.
3. Make sure the checkbox for Camera is selected. 
4. Click App Limits in the sidebar. If you need to use your camera with an app in the list, make sure the checkbox for Limits is not selected.

Give apps permission

If your Mac is using macOS Mojave or later, choose which apps can use your built-in camera:

1. Choose Apple menu  > System Preferences, then click Security & Privacy.
2. Click the Privacy tab, then click Camera in the sidebar.
3. Select the checkbox next to the apps that you want to use your camera in. You might be prompted to quit and reopen an app before it can use your camera.

Try another app

Try to use your camera in another app. For example, if you can't use your camera in FaceTime, open Photo Booth.

Reset the SMC

If you still can’t use the built-in camera and you have an Intel-based Mac, resetting the SMC might help. Learn how to reset the SMC on your Mac."

Here is a great article for help with FaceTime not working as expected on your Mac: If FaceTime isn't working on your Mac

For help with Photo Booth check out this article: Take a photo or record a video in Photo Booth on Mac

Thank you for using Apple Support Communities.

Take care!

The camera on my MacBook Pro was doing this.

Restarting the Mac solved the problem ... until the next time.

Hoping that updating the MacOS last night has helped ... we'll see

All the best :-)