Are you using (either of the) IP addresses to connect or the hostname (from the search)? If from the search, try entering in (either of the) IP addresses

You may also want to fire up a command window, then ipconfig, to see what is showing the extra IP address.
Lastly, this is still the best resourse for troubleshooting MP connection issues:
https://support.stardock.com/space/SHC/1287946260/Multiplicity+Connection+issues+101
Sean Drohan
Stardock Product Lifecycle Manager