Not working with Remote Web Workplace


I’m sure this is a dumb question but I am trying out Duo on a Windows 2012R2 server running the essentials experience and remote web workplace. I setup a new Duo account and Microsoft RD Gateway. I installed duo-rdgateway-2.3.0.msi onto the 2012R2 domain controller. All the settings are out of the box, nothing special. I added users in the duo dashboard. Now I cannot RDP into the server or the workstations.
I get an error message “Your computer can’t connect to the remote desktop gateway server. contact your network administrator for assistance”

What am I missing?