No heat call for Clubhouse unit that serves gym area. Found heater off on lockout, exceeded maximum number of ignition attempts. Cycled power and found a bad flame sensor. Replaced the part on site with OEM part. Completed a routine cleaning/maintenance on unit. Cleaned and removed insulation/debris from burners and burner compartment. Replaced filter. Checked all controls. Cycled system from thermostat several times and it is currently operating properly.