Macbook Pro Retina camera not recognised

My camera has suddenly disappeared! It doesn't work in Skype or Zoom or Photobooth, and when I search for it in the Applications folder, (System information) it says "No video capture devices were found."

I have tried the SMC reset and that didn't work either. Pretty worried because I need this for my work!

Finding most advice online impossible to understand as I'm not very technically minded, and am currently living on an island with very little in the way of IT support (definitely no Apple Stores!)

I'd love it if someone could help me work out what might be the problem. I have also been having issues in the past few days of the computer not turning on sometimes, so I wonder if it is linked.