B vent configuration of direct vent propane heaters

Check power at gas valve should have 24 V AC since you have a thermal pile if present bad gas valve if not open limit or safety upstream follow the loop to find the open.

I think the pilot flame sensor is tired

solution
Amana Furnace Toronto

Unfortunately, Empire Comfort Systems hasn't made that wall heater in years. Never the less, you may get lucky by calling Empire direct @ 800-851-3153 and ask for Technical Service. Maybe one of the old timers can help you out.

you will need a propane conversion kit designed for that particular model heater.
which would most likely consist of a heavier spring for the gas valve and orifices for the burners depending on how many burners you have.
Most all gas heaters come thru the factory set up for natural gas and most have a kit available for conversion to LP (Propane) You will also need a manometer or a gas pressure tester to check the incoming and outgoing pressures from the green (2ndary )regulator outside your house to the gas valve inlet side,usually 11 to 14" WC( water column) pressure( static) 14" being MAX!!
Outlet pressure with burners running 10-11" WC approx. This info should come with the conversion kit if available. If you are not comfortable working with gas then find someone who is, for safety reasons.

Is this unit originally set up for natural gas? If so, the burner oriface and the gas valve need to be retro-fitted to propane. This is something only a qualified service technician should attempt as an incorrect retro-fit could cause an explosion resulting in someone getting hurt or even killed.

what is the model # for the furnace. You are going to have to change the pilot orofice and gas valve for natural gas also.

I've seen excessive draft draw the pilot flame away from the thermo couple when the burners light so when the burners shut down so does the pilot.

burners burning yellow , in complete combustion , blocked air ways to burner , it needs a service soon as poss

You have a crack in your heat exchanger and it is sucking in products of combustion. Replace the heater. OR there is a blockage in the intake or exhaust vent. GET IT FIXED OR REPLACED!