We run AD at a functional level of 2008 R2, but also have servers running 2012 and 2012 R2. We were running on the grace period for Terminal Services 2012 device CALs, because I hadn't had time to install the 2012 CALs that I'd purchased. On the day that the grace period expired (of course), I created a license server, on a 2012 machine, and installed the CALs. The 2012 servers all worked fine. The 2012 R2 servers, however, couldn't find the license server.
When I ran the "RD Licensing Diagnoser" and pointed it at one of the 2012 R2 servers, it broke and gave me an error message.
I checked the "Built In" AD security entry for "Terminal Server License Servers" and all my RD license servers were listed.
After a day of playing around, I went to the group policy editor (thanks to another article) and set the terminal license server search order in "Computer Configuration\ Administrative Templates\ Windows Components\ Remote Desktop Services\ Remote Desktop Session Host\ Licensing".That fixed my problem.
Any thoughts on why the initial install of my 2012 R2 servers exhibited this problem?