Last week I tried to connect to a Windows 2012 server with the Microsoft Remote Desktop Client (2.1.1). This failed with an error: “You were disconnected from the Widows-based computer because of problems during the licensing protocol.”

I’ve searched online and some people suggest installing a beta version of the Microsoft RDP Client (version 2.1.2 or 2.12). This is not yet release by Microsoft but available from several sites. Before you try this, make sure the md5sum is consistent with known good versions.

I did try this version, but it did not make any difference. I tried switching to Cord, as this was working for some people. For me, again, it was not. This might be due to the version of Windows I was connecting to, which is Windows 2012 Server with the Licensing server enabled to allow multiple simultaneous logins.

It seems like Windows 2012 is configured by default to use NLA (Network Level Authentication). The only way I could connect from my Mac to this server is by disabling NLA in the group policy on the 2012 server:

Disable the Require user authentication for remote connections by using Network Level Authentication Group Policy setting.

This Group Policy setting is located in Computer Configuration\Administrative Templates\Windows Components\Remote Desktop Services\Remote Desktop Session Host\Security and can be configured by using either the Local Group Policy Editor or the Group Policy Management Console (GPMC). Note that the Group Policy setting will take precedence over the setting configured in Remote Desktop Session Host Configuration or on the Remote tab.

from: http://technet.microsoft.com/en-us/library/cc732713.aspx

other reference: http://frankdenneman.nl/2013/02/13/using-remote-desktop-connection-on-a-mac-switch-to-cord/