Cycles Render is all Black
I have broken my submission horrifically just at the point I was going to submit it. All my cycles renders are now black . I checked the lights are on and they seem to be. I put a sun inside the room and it's still black. The render times are also massive even on 1 sample in viewport.
Any ideas what I might have done wrong ? I'd rather not lose what I've done. I could go through every object appending materials to a fresh copy of the file but that seems like overkill for what is probably a really stupid mistake.
Thanks in advance for the help.