I upgraded several workstations .. one from 8.1 and another on an HP laptop from win 7 , as well as a fresh install of win 10 on a third., all 64bit machines. After a lot of hassle I got the homegroup working on all but the machine that was on w7 earlier ... (It worked before the w10 upgrade with the homegroup).

When I try to join it, it tells me the machine can't be added. Then I run all the homegroup diags, network diags, checked services, etc. No matter what I try, the machine upgraded from w7 won't join the homegroup. There must be a way to get it working, but everything I've tried has led nowhere on this one machine.

First it tells me "You've been invited to join a HG"
click on join
indicate all the sharing options
enter the password
Then it says "Can't set up a HG this computer"