Itunes sees, but won't load other user's shared library
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.