So I'm working on . stupid noob question of the day here but I'm absolutely stumped. I was doing a tutorial on mist and volumetric lighting and only 1/2 following along and all of a suddenly I can only render in viewport. When I set up a render rather than a viewport preview render I get nothing but a black screen. The programme no longer goes round and collects and syncs the files, theres no little square boxes developing a picture.....nada! What button(s) did I hit that turned off the render function? What did I do? I've rebooted the whole system, I've gone back to previously saved files that rendered fine before .......seriously nothing......well a 5 second pause and then a black frame.