We moved into a house with an old Homart furnace. For 4 years it's been fine, but now the furnace doesn't want to stay lit. There is a little metal box with a dual button. It is a silver button with a red button in it on a box. The red one is supposed to stay down. We held both down as it says to, but for some reason the red one keeps popping up. What can we do to remedy this?