**Work Performed:** Diagnosed 2009 Lennox 2-stage furnace not operating when thermostat was calling for heat. During active call, checked for error codes — furnace displayed no active faults, only standby. Verified thermostat wiring and connections at both the stat and furnace; all wiring appeared in good condition. Reset furnace power and system started operating. Monitored full heating cycle and tested combustion, flames, burners, blower operation, electrical connections, pressure switches, and condensate system — no major issues noted. Attempted to recall historical error codes, but the control board showed none stored. **Findings:** * Furnace started and operated normally after power reset. * No active or stored error codes on board. * All mechanical and combustion components functioning within normal parameters. * Possible intermittent issue with control board — may be due to a stuck relay or internal fault. **Recommendations:** * Advised client to reset furnace power if issu