Tjernlund power vanter

Levie

Hi guys I have an interesting question.  I have two boilers and a water heater connected to a HS2 tjernlund power center with 2 x mac1e extension boards.
I was told by the manufacturer that I can wire the two mac1e together so I spliced the five wires going to the mac1e and connected them to each other and to the main board.
Now here is where It got interesting the main board function properly but when I sent a call for heat to any of the auxiliary boards the yellow LED would show that the call for heat is there but it would not turn on the fan. When I disconnected either one of those boards The other board would work so there is no issue with the boards but it seems like they can't work together.  I spoke to the manufacturer and they can't understand why it wouldn't work do any of you have experience with this?
Tnx
Levi