The answer to 'my boiler won't turn on' is that there could be several common causes, such as a tripped circuit breaker, low water level, or a problem with the thermostat or control board. The symptoms may include the boiler not firing up at all, the pilot light being out, or the boiler cycling on and off frequently.
Some potential solutions you can try DIY include checking the circuit breaker, ensuring the water level is adequate, and verifying the thermostat is set correctly. However, if the issue persists or you're not comfortable troubleshooting the problem, it's best to call in a professional HVAC technician to diagnose and repair the boiler.