Glad it works now.  :)

But your experience isn't weird at all. The gauge which initializes the Civa INS in the panel.cfg coming with the plane is this one.
gauge04=../civa/INS!Config,         0,    0,  0, 0, csx701

It's located in the simicon panel (that small popup with the buttons for the other popups), which is a 2D thing. So as long as this small panel isn't used, the whole Civa gauges won't initialize and therefore stay dark.
So wherever this gauge is placed, it has to be opened at least once to allow the INS operation. Place it in the Vcockpit section for example and it works right out of the box, because the VC is the first thing you see when loading the 707.
Otherwise, just remember to always open the simicons panel once, which triggers the same.