Hi Santino,
Have you had it working before, or is this first time?
The reason for asking is that the flow rate of the boiler (12LPM) is quite high. Could it be that you haven't got enough water flow at say 2 LPM to start it?
The boys seem to prefer the fogwash which I understand is 6LPM and some have 8 LPM but I haven't heard of any 12 LPM.