I've got two computers, A with Windows 7 Home Premium, and B with Windows 8.1. Both are using the same account. A can "see" the library in B, but B can't see the library in A (it doesn't show up in the left panel in iTunes).
When I run in both PCs the command
telnet 127.0.0.1 3689
I get that port 3689 (required for this feature) is open.
- Both are using the same router and are joined to a HomeGroup.
- iTunes version 18.104.22.168 on both computers.
- EDIT: I tried "seeing" the library with another computer running Windows 7, and it can see the library in B but not in A... which suggests it's an issue with computer A.