Baxi Combi 133 HE Plus replaced PCB but no CH?

Hi,

Problem started when fuse has gone on PCB.
I have replaced PCB with new item. Hot water is working but CH is not working. Carried out fault diagnostic and it points to faulty PCB. Asked 2 Gorgi registered engineers, they told me the same after fault finding.
This is now 3rd PCB but still same result, hot water but no CH.

Could it possible to have 3 faulty PCBs from 2 different shop!?