Can use RD Gateway to access servers - not desktop

I am connecting via Server 2012 Essentials from a Win8 pro box. I can create and connect to 2003 and 2013 servers via RD Gateway. I cannot connect to Win7 desktops using the same parameters. If I use the RD app from Win8, I can connect to both. What is different in the way you do it vs. the way Microsoft does it?

This is a really neat app. Sort of like a 4000 blade Swiss Army Knife that I need a wagon to carry around. <G>