Issue with builtin phone Hybrid

I have a small non-profit station that I support. We recently moved there whole operation in a new studio. One of the studios uses an Atlantis Broadcast console(built by Nicom). They had never used the builtin hybrids on this board. Partly because they have a digital phone system. I was able to determine that the phone system has the ability to have analog extensions for things like fax machines, modems and such. I setup one of these extensions to connect to the hybrid.

It seems to work... I can send Master bus audio to the caller. I can hear the caller on the PFL bus(pre fader). I can't hear the caller on the master bus when the hybrid is assigned to it. I can record into Adobe Audition and I can see the caller audio is there, way down in the weeds at about the -40 to -30 level.

My goal is to get this working and take advantage of the builtin mix-minus on the console. The way they had it setup before they didn't have this. I can setup a small side mixer and get the same results, but this will add more work for the board op and more equipment on the desktop.

This is not the best board but it is what they have to work with. I have looked in the limit manual for this board and can find no reference to any kind of gain level to boost the caller to master bus level. Maybe there is an internal adjustment for this? Hoping someone else has some experience with this console.

Ok, I figured out the issue with this board. There is an option that is not well documented in the manual. The only place it is shown is on the hybrid schematic(see attached photo). I'm assuming that it was supposed to be configured like this from the factory. The jumpers are supposed to be configured one way for the first hybrid and another for the second hybrid. Since both of these were configured the same way the mix-minus from the other hybrid was killing the audio on the master bus.