The answer to 'my heat pump won't turn on' is that there are several common causes, including a tripped circuit breaker, thermostat issues, refrigerant leaks, or a problem with the compressor or other components. The symptoms you may notice include no heat or cooling, the system not powering on, or strange noises or smells.
Before calling a professional, you can try some basic troubleshooting steps like checking the circuit breaker, replacing the thermostat batteries, or cleaning the outdoor unit. However, if the issue persists or you're not comfortable diagnosing the problem, it's best to call an HVAC technician to properly inspect and repair the system.