CO2 high

CO2 incubator that I inherited does not seem to have a functional CO2 gas controller. The incubator reads "0.00" and alarm for HIGH blinks and beeps regardless of calibration and setpoint attempts. FYRITE reads no CO2 in the incubator... Any help? Best regards Hamid Omidi (Mr)

Equipment: Napco 6000 CO2 incubator