Hi we have a netaheat 10/16 with the 407676 pcb board
when we turn it on the pcb board clicks but there is no spark and doesnt seem to be any gas. Have checked electrode and connections which are ok is the board U S or could it be the gas valve ??
Possibly stuck air pressure switch. With power off remove one of the tubes and blow down it to see if it clicks, do this a couple of times then reconnect and try the boiler. Sometimes it can just get stuck or may need replacing altogether,