Okie dokie .
We're trying to save you the cost of a callout, as it "may" be something very basic! But, if all valves are open and you've tried a reboot, then it gets more in depth and likely requires a chargeable visit!
It's possible that the power cut has blown the external programmer which could be bridged out to ensure a CH demand to the boiler, but this is likely beyond your skill set (NOM).
