Any time a complete group stops firing out of the blue on those machines, especially after maintenance, a fuse blew on the head board. The good news is it's fixable without having to buy a whole new head board. Before you get it repaired though make sure you check all of the cables that go to the head and make sure they are not damaged or partially plugged in. You want to find the reason the fuse blew in the first place. It could be as simple as you bumped the head cable slightly when changing dampers and that would do it.