Not the case in this thread, but often the reason for a non-functioning shutter is a peice of film wound into the shutter curtains (cut the leader SMOOTHLY with no edges than can break off into the shutter).
It is sometimes possible to repair this particular problem by taking the camera shutter assembly out of the housing (aluminum part with the vulcanite on it) and without further disassembly, fish the film chip(s) out with a pair of tweezers. I managed to do this sucessfully outdoors in a campground once during my student days - the IIIc was the only camera I had or was likely to have for a long time.