Read this complete Knowledgebase articles and know how to allow multiple RDP Sessions for Single User.

Server 2012/2008 R2 unlike their predecessors, comes with the multiple remote desktop session restriction enabled. If you are only connecting to a server for remote administration purposes that can get a bit annoying, especially if you have a generic administrative account that multiple techs are using, and you keep kicking each other off the server.

Just as with earlier versions of Windows server you CAN have two RDP (remote desktop) sessions at any one time, the restriction is one logon for one account. Thankfully you can disable the restriction and there are a number of ways to do so.

Server 2012 and 2008 R2: Enable Multiple RDP sessions via the registry

1. Start > in the search/run box type: regedit

In regedit navigate to:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server