The answer to 'emergency HVAC service not heating' is that there are several common causes, including a malfunctioning thermostat, a problem with the furnace or heating system, or a lack of airflow. Symptoms may include the HVAC system not turning on, the home not reaching the set temperature, or the system blowing cold air.
Some potential solutions include checking the thermostat settings, replacing the air filter, and inspecting the furnace or heating unit for issues. However, if the problem persists or you are not comfortable troubleshooting the issue, it is best to call a professional HVAC technician who can properly diagnose and repair the system.