ProjectServer.OpenProject fails in Taskscheduler

Hi,

while running my Trados app by double click, app works as expected. 

But as soon as I put this task to Windows Task-Scheduler, ProjectServer.OpenProject raises an Exception:

Code:

var tradosProjectServer = new Sdl.ProjectAutomation.FileBased.ProjectServer(this.Host, false, this.UserName, this.Password);
string projectId = myProjectId;
var project = tradosProjectServer.OpenProject(new Guid(projectId), workFolder);

Exception:

There was an error opening the server project
   at Sdl.ProjectAutomation.FileBased.ProjectServer.OpenProject(Guid projectId, String localProjectFolder)

While any other things like working with local projects work as expected, here app fails.

Is there an issue with this function, when process is running without UI?

 

Credentials: checked

 

Thoughts? Thanks

Markus