If I re-configure the control to use the xxxxxxxx.ddns.remoterig.com address as the SIP address. It will not connect. I hear three tones (beep, beep, beep) in the headphones of the control over and over. I even tried to move the control unit 100 miles away so that I was on a different network. Same result.
Having been given a tip by the ham I bought the boxes from, I found that my issue was my firewall settings weren't properly configured.
I also found that my UDP ports were set to the old values 12000,11000,5060, even though I had upgraded to the v2.95 firmware.
I re-assigned these to new port numbers.
The hardest part was figuring out the best way to pass these UDP ports through my ATT router. The IP Passthrough worked, but it completely exposed the RemoteRig device to the public internet. I ended up defining four "gaming" services to map the UDP ports, and assigned them to the RemoteRig local IP. That worked.