Windows Server 2012 - Accessing RDS via web access from external address

I had this issue, it's all down to names and certificates. You need to ensure that:

• All servers are configured to present your External DNS name, RD Web Server, Session Hosts, brokers and Gateway (if you have one)
• Servers need to be able to respond to that External name on the internal network, so you will need to setup a second DNS zone on your Internal network, with the external name and correct IP's for all servers
• Ensure that all servers have a valid certificate for the external domain. You will likely need a wildcard for this as you need all servers presented as servername.external.domain