Cannot get Primary computer to connect

I've posted these messages to Support but maybe I'll get a quicker, and better, response here.  

"I've spent an hour on this. I'm trying to connect two computers on my home network. I can't get it to work. 

I bought the Object Desktop product. Installed all the apps. Ran Multiplicity on two computers with one as primary and the other as secondary. Added the secondary to my primary with the code. Multiplicity on my secondary appears to be connected (at least the taskbar icon is blue). On the primary the Multiplicity taskbar icon is grey and says "(disconnected)". 

"I've tried turning off my firewall, restarting the PC, restarting Multiplicity. I can ping both computers."

"... and I've uninstalled and reinstalled Multiplicity."

"Well that's interesting. When I switch my Primary computer to a Secondary, it connects to the network. Switch it back and it disconnects. I guess getting this to work is going to be my weekend project."

 "... and I've rebooted my router."