If your Smoke and Heat Sensor is reporting offline or malfunction, it means it has not communicated to the control panel within 24 hours. Check the history of your sensor for any Low Battery signals. If there is a Low Battery, change the batteries on the Smoke and Heat Sensor and the Malfunction will clear. If it doesn't, ensure that the sensor is within 100 ft of the Control Panel. If the sensor is within range but still in malfunction, please contact Customer Support.