Why does the flame in my gas fireplace go out after closing the door?
You need to have a way for air to get IN to the fireplace as well as a flue for the gasses to get out. If the front and door is sealed up too tight, the flame consumes all of the oxygen in the fireplace and extinguishes itself. Usually there is a little vent hole or louver in the front that draws air into the fireplace, or there is a pipe coming from the outside supplying air. If that pipe got blocked by something, that would do it.