The answer to 'carbon monoxide detector not working' is that there are several common causes, including a dead or malfunctioning sensor, a power issue, or improper installation. Symptoms may include the detector not powering on, not sounding an alarm, or displaying error codes.
To troubleshoot, first check the batteries and replace them if needed. Ensure the detector is properly mounted and not blocked by furniture or other objects. If the issue persists, the sensor itself may need to be replaced. This is generally a job for a professional, as carbon monoxide detectors should be installed and serviced by a qualified electrician or HVAC technician to ensure proper functioning and safety.