We recently purchased a Vermont Castings Victory gas insert. My husband installed it in our fireplace. The fireplace had a gas line from a gas log set someone had installed previously. When we turn on the unit, the pilot lights, then the fireplace lights. Flames flare up from the back burner then there is an obvious click from the controls and the back burner goes out. We cannot get it to turn back on with the remote or any other method. The front continues to burn a low/moderate flame. Everything I've searched talks about cobwebs, dirt, old parts, etc., which doesn't really apply to our new unit. Any ideas on what would cause the unit control to turn off the back burner?