Set Appliance State:

Mains Power Off
CH Demand
Holiday Mode OFF (Button NOT illuminated)
Eco Mode ON (Button illuminated)
Ensure Primary Heat Exchanger is Below 40°C
CH Thermostat to MAX
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Does the burner ignite with a CH demand?
Note:
On some versions the flame can be seen via the viewing window at the top of the heat exchanger.