Set Appliance State:

CH Demand
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Allow the boiler to run in CH mode briefly.
Isolate Mains Power to appliance as per TOP's P4

Remove the diverter valve head.
Inspect the diverter valve spindle, it should be in the fully extended position.
Is the spindle in the correct position?
Note.
Due to the diverter valve cartridge being held in by two plastic clips, it is advisable to drain the primary system water from the boiler before removing the head.