Propane Furnace "LO"

Hello there: The 5 yo Laars Endurance furnace in my cellar stopped itself sometime late on Friday.. It's Model # EBP 110. THere are two tanks outside, 3/4's full, that hold about 120 lbs. or gallons of propane each, I guess. Yesterday I removed all snow and ice from around these tanks. Put blankets on em overnight. Clouds, no sun all weekend, so far to help. Each time I hit the reset button on top of furnace, it goes from LO or lockout to kicking on for awhile, but never coming up to speed, then going into lockout mode again.. My fiance has been at the tanks with my hairdryer this morning, actually at the yellow line leading from the tanks to the thing on the outside of the house. He thought it might be froze up through there somewhere, or a valve frozen up since there's a slight "thump" in the gas line coming in when ya push reset. No changes. Seems like there should be plenty of pressure. I'm a little scared. Please help with your knowledge base. Thanks so much.
Area (Andrea)