The answer to 'why is my heat pump not working' is that there could be several common causes, including a refrigerant leak, faulty compressor, electrical issues, or problems with the reversing valve. Symptoms may include the unit not turning on, poor heating or cooling performance, or unusual noises.
If your heat pump isn't working properly, it's best to call a licensed HVAC technician to diagnose and repair the issue. Attempting to repair a heat pump yourself can be dangerous and may cause further damage if you don't have the proper training and equipment. A professional will be able to quickly identify the problem and get your system back up and running safely.