C# Windows Service - CreateProcessAsUser as a local admin in a user session

Situation A Windows service is running as SYSTEM in the background. The service should start an application in an active user session. This application should be started with the rights of a third user (not SYSTEM, not current user but local admin account). Involved SYSTEM: The service is installed by default without any special configuration. User A: Logged in with an own Windows session. His SessionID will be used to start an application under user B in it. User B: Logged in with LogonUser to Windows. His token is then used for CreateProcessAsUser is used. Current state I have written a function which can start an application in the user session. It expects parameters like: applicationName, commandline and the impersonation information. What is working? Launching an application from a service into a running user session. The application runs under the SYSTEM account or under the same account as the logged in user. What does not work? Launching an application from a service into a running user session. The application should run under another user account. It gets launched but it is not usable (see attached Screenshot) How to call attached code // = Prepare callback helper.AppLauncher.PROCESS_INFORMATION procInfo; // = Prepare impersonation [login to view URL] impersonationInfo = new [login to view URL](); // = 2: Start a process as specified user [login to view URL] = 2; // Service = 0, CurrentUser = 1, LogonUser = [2] [login to view URL] = "theLocalUserWithAdminRights"; [login to view URL] = "myVerySecre1P@ssword"; [login to view URL]("[login to view URL]", null, true, impersonationInfo, out procInfo); Please find here a public description of my request: [login to view URL]