Our file server in the basement had been running Windows 7 up until this weekend, but for the past while it has been prompting to say that I should totally upgrade it to Windows 10 any time now. We moved both of our upstairs computers to Win10 without a hitch some time back (I went from 8.1, and atara from 7). I was just waiting until I had a free weekend so that I could watch its progress.
The upgrade itself went smoothly, and other than losing a couple of programs that I knew in advance were not compatible, everything seemed to be working fine from the get go. I say "seemed to be" because I quickly discovered that the file sharing was not working at all. Since the whole purpose of this computer is to be a file server, it becomes very inconvenient when file sharing doesn't want to work.
My desktop and the file server could see each other on the network, but even though I could get at the files and open a remote desktop from the basement to my main machine, the reverse was not true. The file server was listed among machines on my network, but if I tried to get to the shared folders, or open a remote desktop, my computer warned that it could not find the other machine on the network.
I did some reading and experimenting off and on over the weekend, playing with everything from the firewall and sharing settings on the file server, to tweaking the settings in the router. I discovered that a few others had been reporting an identical issue, and some reported that joining both machines to the same HomeGroup solved it for some. I ran into frustration on that front as well because it seems that I may have set up a HomeGroup under Windows 8, and its uncooperative ghost was still hanging around doing no good for nobody.
Finally, I managed to connect to the machine by opening a remote desktop by its internal IP address. I still had to specify the machine's network name to log into it, but it was finally working. I got the file sharing working the same way: \\192.168.x.x\Raid_One\ and then signed in using the machine's network name, user id and password. It's a bit cumbersome, but it works.
When I mentioned how much trouble it had been giving me, atara tried connecting from her machine, and it worked on the first try. She turned on discovery, the file server popped up in her network listing and it let her right in. Well then!
The same site that led me to trying to use the combination of IP address and machine name suggested that it was a bug in Windows 10 that manifested when one machine used a Windows Live ID to sign in, and the other did not.
I use my Windows ID so that I can keep my desktop and Surface in sync, but the machine in the basement does not have one, and atara syncs things on her own terms. Since the problem only manifested when I converted both machines to 10, that gives some credence to the explanation about it being a bug. I don't like connecting via the IP because, well, they're dynamic and stuff. I suppose I could hard wire the IP in the basement machine, but I would prefer for the networking work properly. I don't like running on a kludge.