Set Appliance State:

Mains Power Off
Gas Off
CH Demand
Central Heating Switch in constant position
Boiler Switch in ON position
Ensure boiler is cool
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

After a few seconds delay does fan run?
Note:
Boiler may go to lockout.
Switch OFF power and push reset button to cancel lockout.