Camera - green light on, but no one home!

Hi, I just opened FaceTime for the first time in a while, and got the message that there is no connected camera (although the little green light was blinking). I shut down and restarted, and also tried opening PhotoBooth - also no camera. I've done the commands: sudo killall VDCAssistant, and it said 'no matching processes were found'. Also then tried sudo killall AppleCameraAssistant, but nothing happened. Would very much appreciate any suggestions - am due to FaceTime my bestie in New Zealand!

I have a MacBook and recently updated to Mac OS Mojave.

Maybe or may not be related: I had a trovi.com virus (?) the other day, and in my desperation to get rid of it, I deleted all the applications that I didn't recognise... is it possible I deleted some vital camera thing?