Did the network work previously with these settings?
Yes. Worked like a champ for years. Suddenly stopped working out of the clear blue sky nearly a month ago. My first thought is that Windows applied an update that hosed things, but no updates had happened.
Passwords change or anything like that? SOMETHING had to have happened.
This is a total shot in the dark, but have you tried disabling IPv6 altogether? It’s not really necessary (despite what the purists/futurists would say) and it’s one less thing to worry about…
Did Comcast remotely update your router in that timeframe?
Just a thought, but on my router, there’s an option which keeps each device on the network private; the option is called ‘Isolate Member’. This means that the devices can’t talk to each other, which is just what you’re seeing.
He said he could ping the other computers, so that’s not it.
Are you using the same user name accounts that you set the networking up with?
All three computers log in with the Microsoft user account. The router wasn’t updated (at least, not according to the firmware date) and we haven’t done anything to it since we set it up.
This crap is straight out of the Twilight Zone. There is absolutely no reason that I can see for this to be happening…but it is.
Have you tried deleting the shares and recreating them?
I had exactly the same problem and this was the only way to fix it.
Create a new share to any random folder and see if you can connect to it from another box.
Also have a look at this post.
http://www.askvg.com/windows-fix-sharing-tab-missing-in-folder-properties-and-context-menu/
The sharing tab is visible. Everything in the list that it said to do is already on.