Our Lennox G24M4/5X fails to ignite. Thermostat is operational, & activates the combustion air blower; also changes the blink pattern of the LED; When Thermostat is off, LED blinks constantly on/off. Once Thermostat is turned on LED blinks 4 times then shuts off, this repeats every 5 seconds. Manual fails to provide diagnosis for 4 blink LED fault message. Suggestions appreciated.