The answer to 'my boiler won't turn on' is that there could be several common causes, such as a tripped circuit breaker, a malfunctioning thermostat, low water pressure, or a problem with the boiler itself. Symptoms may include no heat coming from the radiators, the boiler not firing up, or error codes displayed on the unit.
Some simple troubleshooting steps you can try are checking the circuit breaker, ensuring the thermostat is set properly, and verifying the water pressure in the system. However, if you are unable to identify and resolve the issue, it's best to call a professional HVAC technician, as boiler repairs can be complex and potentially dangerous if not handled properly.