Win32 Error System.Runtime.InteropServices.SEHException when using CreateProcessAsUser in C# Windows Service

Question

I'm working on a C# application on Windows 11 (version 23H2) that aims to create a user session (remote desktop session) from a Windows service. The goal is to launch an application within that session and then terminate the session.

Here's where I'm encountering issues:

APIs Used:

• LogonUser (advapi32.dll): This seems to be working fine, presumably creating the user session.
• DuplicateToken (advapi32.dll): Successfully duplicates the obtained user token for application launch.
• CreateProcessAsUser (advapi32.dll): To launch the desired application within the newly created session and This is where things go wrong.

Errors:

• Launching Calculator (@"C:\windows\System32\calc.exe"): Throws a System.Runtime.InteropServices.SEHException with the message "External component has thrown an exception."
• Launching Notepad (@"C:\windows\System32\notepad.exe"): Throws a System.ComponentModel.Win32Exception with the message "The system cannot find the file specified." (Interestingly, this path works when launching from the command prompt.)

What I Expected:

CreateProcessAsUser to successfully launch the specified application (Calculator or Notepad) within the newly created user session.