The answer to 'boiler not heating' is that there are several common causes, including a faulty thermostat, low water pressure, a malfunctioning circulator pump, or a problem with the boiler itself. Symptoms may include the boiler running but not producing heat, or the home feeling cold despite the boiler being on.
Some potential solutions include checking the thermostat settings, bleeding air from the system, or resetting the pressure. However, more complex issues like a faulty circulator pump or problems with the boiler itself will likely require the expertise of a professional HVAC technician.