Finally after some testing and comparing with the working INS on my Captain 727 I figured out what was the problem.

A simple missing line from the panel.cfg (which was provided with the package)

Here goes:

[Window06]
size_mm=250,196
background_color=16,16,16
window_pos=0.300, 0.070
position=0
visible=0
ident=11041
no_luminous=1
gauge00=../civa/INS!Config,         0,    0,  0, 0, csx701
gauge01=../civa/INS!Cdu1, 0, 0, 250, 196

The file csx701.Isd is not created in the CIVA folder when this line is missing, and this is preventing the gauge from initializing....