How can I get this working?

I have a Biaisi M90F 24S Combi Boiler. It does not fire up.
All it does is spin the pump then stop.
I have checked all the Micro Switches, the exhaust fan, the pump, gas valve, diverter valve etc, they all work OK. It appears that they are not talking to each other.
I am in France, lots of head scratching by plumbers? etc. Spoke to Biaisi Technical team they think it may be the PCB 's [cost 274.37 pounds plus fitting] so hence the question any ideas? please