The previous version of Synergy handled my situation quite well. I have a machine at home which is not on a work VPN but is on my home wi-fi network. I also have a work laptop which is on the same wi-fi network but on the work VPN. When I fire up Synergy it refers to the home machine as imac.local (much as with the previous version of Synergy) but the work machine is referred to as sschrate-1.corp.<my work domain>.ad.
At a guess, since I'm accessing the Symless login over the VPN on one machine and not via the VPN on the other, the two machines cannot see each other despite sharing