Hlastead Finest Gold Condenser Boiler - OVERHEAT LOCKOUT?

For a few years my Halstead Finest Gold Condenser Boiler stops working. It does not heat up the water. I notice that the IGNITION LOCKOUT is red. Also that what I assume is a fan is not working as there is not a louder wirring noise which usually accompanies the hot water system. I have had sensors replaced but problem still occurs daily. Thanks Angus