I've had this RS-80N3 for a couple of years and have used it many times without problem. Last night while making some long exposures on my 5D mkIII it would focus fine using the remote, but the remote would not trip the shutter. It was achieving focus fine using autofocus, but just would not trip the shutter. Tried manual focus and same deal, it would not fire the shutter. The shutter button would operate fine when used without the remote.
I've tested it today in the bright light of daytime and the same thing happens. I've tried the camera with another remote I have, a generic brand intervalometer, and everything works fine -- the camera will focus and the shutter will fire using the intervalometer.
Could the RS-80N3 suddenly have developed a broken wire, or am I overlooking something obvious?