this is a great add-on, I just added it this winter, as for why yours quite running, I have no suggestion for you, except for the fuse which Dawg suggested, Dawg knows what he is talking about so that is probably what it is!
I had a few problems with mine for a while but it was always just a wire coming loose. That thing is in a spot that naturally gets pulled on when the suspension is used. I would just suggest to go through the wiring and make sure it is all hooked up. They are really reliable units.
As for the guy who said to get off and open the door.... WOW. Why bother even logging on?
Mine stopped working and I got a tip from another member, unplug it from the wall for a few minutes so it can reset, mine worked after that little trick.