Had power outage this week, out for 12 hours. When I came home from work furnace was not working, went and flipped switch for furnace to off, check the circuit breaker, check the thermostat. Everything seem fine. Turned on the switch for furnace, also thermostat, could hear the clicking for a little but the usual sound of the furnace igniting did not come, clicking continued a little more. Also, on my 14 year old lennox furnace I could see a fast flashing green light, none of the material given to me when I brought furnace suggest what to do other then call service repair man. What would be something I check before I have to call repairman

Thank you

Often there is a key to the blink code on the inside of the blower door.