I am suddenly unable to refill the circuit of my Worcester 24 CDi boiler. I have done it lots of times during the 10 year life of the boiler and never had a problem Now, when I insert the key and lock it and then open the refill knob, I can hear the water initially flowing by hitting and locking even more the key, but no water then flows further. The pressure indicator does not move. Is there any other valve that can prevent the circuit to be filled?
Thank you