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?