The Windows 8.1 machine was the problem. I went to the
CONTROL PANEL, then to
NETWORK AND INTERNET, then to
NETWORK AND SHARING, then to
ADVANCED SHARING SETTINGS, then
HOME GROUP CONNECTIONS - I changed it from the "recommended" setting of
ALLOW WINDOWS TO MANAGE CONNECTS
and instead choose
USE USER ACCOUNTS AND PASSWORDS TO CONNECT TO OTHER COMPUTERS
Instant SUCCESS as all the other computers share directories were instantly available.