RTF,
I think your ICS may be OK.
I assume that there are no warnings and this is with the engine running at normal NR?
If on the ground and engine stopped you will have several warnings obviously.
No doubt you are aware that in the B3 you are obliged to have 2 functioning headsets ( Pilot and Co-Pilot) and ICS as per RFM Limitations.
The Pilot ISO is just doing as it should - isolate the ICS.
I would guess that your warning unit and/or sensor that talks to the warning unit is duff.