Alistair,
It could just be a hardware malfunction, and in that case you’ll need to contact RICOH support directly. https://theta360.com/en/support/contact/
Couple ideas, though, depending on how much you like trying to fix things yourself.
I believe you can hold down the WiFi and shutter buttons while you plug in the USB cable to enter Mass Storage mode. You can then look at what files are on your camera. I can do this on my THETA S. I don’t have an SC, though, so I’m not 100% sure it’s the same. This isn’t a fix for your problem, but it might be reassuring to see what files are on the camera.
Another possibility is firmware. You might need to upgrade. It shouldn’t be hard or scary. This is old information and a completely different model, so definitely take it with a grain of salt. But it might give you some ideas for making sure you’re using the most recent versions of the Mac app and the camera firmware:
http://theta360.guide/blog/camera/2016/01/20/fixing-bricked-theta.html
Hope it helps,
Jesse