Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Turn Hot Water Tap On
Remove the diverter valve head from the diverter valve body
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Inspect the position of the diverter valve spindle.
Is it in the fully extended position?