The answer to 'my emergency HVAC service won't turn on' is that there are several common causes, including a tripped circuit breaker, a faulty thermostat, or a problem with the HVAC unit itself. If your HVAC system won't turn on, the first thing to check is the circuit breaker. Make sure it hasn't been tripped and reset it if necessary. You should also check the thermostat to ensure it's set to the correct mode and temperature. If those basic troubleshooting steps don't resolve the issue, there may be a more serious problem with the HVAC unit that requires professional service.
If the circuit breaker and thermostat checks don't fix the problem, it's best to call an HVAC technician to diagnose and repair the issue. HVAC systems can be complex, and attempting to repair them without the proper training and equipment can be dangerous and may even cause further damage. A qualified technician will be able to quickly identify the root cause and get your HVAC system up and running again.