Mac 'camera not detected' or 'not available'

You need to reinstall macOS.

Reinstall El Capitan or Later Without Erasing Drive

Please be sure you back up, if possible.

1. Restart the computer. Immediately, at or before the chime, hold down the Command and R keys until the Apple logo and progress bar appear. Wait until the Utility Menu appears.
2. Select Disk Utility and click on the Continue button.
3. Select the indented (usually, Macintosh HD) volume entry from the side list.
4. Click on the First Aid button in Disk Utility's toolbar. Wait until the Done button activates, then click on it.
5. Quit Disk Utility and return to the Utility Menu.
6. Select Install OS X and click on the Continue button.

If this doesn't fix the problem, then run the Apple Hardware Test to determine if the camera is still functional: Apple Hardware Test. You may need to have it replaced after the stores re-open.

Make an appointment at the Apple Genius Bar for service. If you need to find an Apple Store - Find a Store - Apple. Also, see How to find your nearest Apple Authorized Service Provider (AASP) or Distributor (AAD).

Does this method mean that in theory your software installs (Office, Photoshop etc) and Files will stay in tact?

Yes. Only system software is replaced. But you should still make a current backup just in case.

Thanks for the feedback!

I'm setting up Time machine for a backup as-well as a cloud backup of my files before i'll try this.