I have installed the Remote Desktop Servces role on a Windows Server 2012 r2 standard and did the following:
1.Enable Multiple RDP Sessions
2.Log into the server using Remote Desktop.
3.Open the start screen (press the Windows key) and type gpedit.msc and open it
4.Go to Computer Configuration > Administrative Templates > Windows Components > Remote Desktop Services > Remote Desktop Session Host > Connections.
5.Set Restrict Remote Desktop Services user to a single Remote Desktop Services session to Disabled.
6.Double click Limit number of connections and set the RD Maximum Connections allowed to 999999.
Afterwise I run gpupdate and restarted the server.
When the server was back online I still caný logon to the server with more then 2 users.