The answer to 'my emergency HVAC service won't turn on' is that there could be several common causes, such as a tripped circuit breaker, issues with the thermostat, or problems with the HVAC unit itself. Symptoms may include the system not powering on at all or the fan not running.
If the issue is a tripped circuit breaker, you can try resetting it. However, if the breaker keeps tripping, that indicates a more serious electrical problem that should be addressed by a professional HVAC technician. Similarly, issues with the thermostat may require replacement or reprogramming, which is best handled by an expert. For problems with the HVAC unit, it's generally recommended to call a professional for diagnosis and repair, as improper DIY work can be unsafe and lead to further damage.