Hi , what boiler do you have?
Hi . will need the GC number, pro3 is not listed .
Ok , no probs. As to your problem , if the boiler was running when the controls/ power as turned off , this could have caused an overheat situation with nonpump running to clear the cheat from the boiler , cutting out the overheat stat. Try turning off completely for 10 mins , then back on , unless there is a dedicated reset button on the boiler