KB article (2802436) related to installing RDS on Windows Server 2012 where the Firewall service is not running.
“…On a computer that is running Windows Server 2012, when you try to install the Remote Desktop Services Role, using the "Add Roles and Features" Wizard, the installation may fail. Additionally, during the installation process you may receive one of the following error messages:
Unable to open remote connections on the RD Connection Broker server
The post installation configuration did not complete.
Note: After a reboot the RDS Server may work. If it does not, the following powershell commands will complete the failed action:
$tss = Get-WmiObject -namespace root\cimv2\terminalservices -class Win32_TerminalServiceSetting
During the post installation configuration, the wizard attempts to enable necessary firewall exceptions for the RDS Role. When the firewall service is stopped, this operation fails and is reported with the above error
It is not recommended to run without a Firewall. If you have certain requirements to do so, enable the Firewall Service at least during installation of this Role…”