Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Diverter valve located at the lower LH side of the appliance
Remove Head from body by removing retaining clip located behind the actuator head
Boiler CH thermostat to MAX
CH Demand
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Is the diverter valve in the CH position (Spindle retracted)?
Note:
CH position - Spindle retracted inside.
DHW position - Spindle extended out.