When connecting with a Mac using RDP (Remote Desktop Protocol) on a Windows server, you might encounter a message saying “You were disconnected from the Windows-based computer because of problems during the licensing protocol”. This has to do with permissions, thou it’s not a problem with your configuration. This is a bug with RDC for MAC Version 2.1.1

Thou there is no solution until now, it is suggested to install the hot-fix below

RDC for MAC v2.1.2 (Early Build Hotfix)

After installing the hot-fix, you will be able to connect to your Terminal Server.