I've been searching for answer to my issue and most of the threads seem to point to it being a certificate issue. I wanted to explain our environment in a little more detail though as I think it may be something else causing this.
Terminal Services Gateway UNC - rdsserver01.domain.local
External Address to Access - http://rdsserver01.domainusa.org/rdweb
Added DefaultTSGateway in IIS as rdsserver1.geneva.local
If I access the server internally (by IP or UNC or external address) I can access remote desktops just fine.
If I go off network, I can access the sign-in page and actually sign in. I created a Self-Signed Cert using rdsserver01.domainusa.org. I can get past the certificate errors. When I attempt to connect using Remote Desktop I get the following message:
your computer can't connect to the remote computer because the remote desktop gateway server address is unreachable or incorrect. type a valid remote desktop gateway server address.
Again, from the threads I've read, they are saying it's a certificate issue. Or is it some thing simpler like some missed setting? If any additional information is needed, please let me know and I will try my best to provide it.