The answer to 'HVAC system not heating' is that there are several common causes, including a malfunctioning thermostat, clogged air filters, issues with the heating element or compressor, and problems with the ductwork. Symptoms may include the system not turning on, poor airflow, or the home not reaching the desired temperature.
Some potential solutions include checking and replacing the air filter, resetting the thermostat, or inspecting the heating element for issues. However, many HVAC problems require the expertise of a professional technician, especially if the issue is with the compressor, refrigerant levels, or more complex components. It's generally recommended to call an HVAC specialist if you're unable to identify and fix the problem yourself.