Extended Stay Propane Tanks and Furance Problems

enrays - part of the problem may be what you described. Part of it may be the combination of altitude and temperature. When the ambient temp gets too low, propane does not want to vaporize. Another potential problem may not be with the fuel, but the air, at 9800ft your oxygen concentration may be too low for the furnace to light properly on the fuel flow you have from the extended stay tank. JMHO.