Thanks for the clarification... appreciated.
At the risk of creating more confusion, I'll repost the following.
In my case, the Win10 computers are visible to the Win8.1 computer and both the Win10 computers can be accessed from the Win8.1 computer.
At the same time, the Win8.1 computer is NOT visible to the Win10 computers and cannot be accessed from either Win10 computer.
For security reasons, the Win8.1 computer is normally logged in as a Non Administrative User. A few days ago, I used an Administrator login on the Win8.1 box and the Win8.1 computer became visible to the two Win10 computers.
Both the Non Admin and Admin logins have identical file sharing settings.
In the hope that this might be helpful in unearthing an answer. I have even considered upgrading the Win8.1 computers to Win10, but, I would really prefer not to.
Thanks again for all of the responses,
Beverly Howard