Raypak 406A won't heat.

Heater goes through it’s normal routine CFH - Spark - Spark - Spark - Heating. Just no heat. Turned off the pump - heater detected no water and stopped. Turned on the pump - normal cycle just no heat. Turned off the propane - heater still says Heating. Turned off heater - turned it back on - left gas off - CFH Spark Spark Spark Heating. Spark sounds were present but faint if that means anything.