I was setting up a PoC with 2012R2 RDSH environment, adding the RDSH hosts to the connection broker.  This went without errors, but when trying to add the servers to a collection I got this strange error:

with an eventid 24584:


As it turns out, this is a cryptic error which only appears if you have an active GPO on the RDSH server which sets one of the following:

• Require user authentication for remote connections by using Network Level Authentication
• Set client connection encryption level
• Use the specified Remote Desktop license servers

Source: https://support.microsoft.com/en-us/kb/3014614
It appears that the issue remains in Server 2012R2, 😐

Unlinking the GPO’s which configured one or all of these settings and deleting all subkeys in: HKLM\software\policies
And rebooting the server fixed this problem for me.