Ctr-Alt-Del to log into Windows Server 2008 R2

Logining in by using the "running man"/sending Ctrl-Alt-Del always worked. Today I suddenly cant get to the Enter User/Password anymore.

For the Logfile:

2017/10/05 12:31:16.519 4344 4368 D1 simulating Ctrl-Alt-Del (with SASLibEx)
2017/10/05 12:31:16.520 4344 4368 D1!! CtrlAltDel::Execute SASLibEx_SendSAS sessionID=1 LE=2, Errorcode=2

Any help is very welcome