I had somebody came and had a look at it, it turned out to be the duffed PCB that I changed. So we replaced with another new PCB, now it works as new.
Thanks for all advice.
I am having problem with my Vokera 20/80 RS flowmatic combi boiler, First it had water leak then water got to PCB, I changed heat exchanger hope to get it work again, the water leak cured but it will not fire up, I notice the fan will not run at all and gas valve not ' clicking'. I changed PCB...