Hot water only when heating radiators.

[Bp89]

Hello. I have a Worcester Greenstar 24 Ri boiler linked to a Megaflo cylinder. The boiler heats water for central heating but when I want hot water only the boiler does not fire up. I can get hot water when the central heating is on, but not ideal in the summer. The boiler is only 18 months old. I have attached images of possible problem areas. Help please.

 

[SimonG]

Controls issue, time to get the testers out or somebody in.