Itunes sees, but won't load other user's shared library
Solution 1:
The errors you cite doesn't necessarily have anything to do with the problem you're encountering. 10.10 (Yosemite) is nearly five major OS revisions old now... I assume being run because your machines no longer support newer operating systems?
All I can really suggest is that you make sure each of the machines are running 10.10.5 and all supplemental updates, and all have the latest supported version of iTunes installed, 12.8.1.