Looking For Clonk Rage Keyfile My Gas Boiler Has Stopped Working...........?

My gas boiler has stopped working...........? - looking for clonk rage keyfile

He paused a moment to work yesterday, I did not know at first, but began to feel cold when I checked the heater was not turned on. I looked out on the boiler and the pilot. I reignighted driver and seems to work, but then began to cut noise and clonking. I tried several times, but it remains the same. What could be and how they can be resolved. I want a gas engineer to call tomorrow, I think it can be expensive ........