PS HarriJaakkonen :~/Blog/Posts> cat ./enable-multiple-rdp-sessions-20082012.html

Enable multiple RDP Sessions 2008/2012 servers.

There are restrictions for a server without activate RDS-lisencing server.

You cant enable multiple rdp-sessions from registry. 

HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlTerminal Server

Find a value fSingleSessionPerUser and set it to 0

Problem solved.