WindowsProcessMBS CreateProcessWithLogonW

I posted this on the NUG list but might get more response here.

I am trying to launch an application from within a Xojo app using WindowsProcessMBS (code below). It is important that I use this function as it calls the Windows CreateProcessWithLogonW and I need to authenticate as this is being developed as a Windows service.
In testing with a console app all works well if I don’t try to authenticate, but when I include credentials, the LastErrorMessage returns “The parameter is incorrect”.
I have reviewed the Microsoft documentation for CreateProcessWithLogonW:

and tried leaving the domain null and passing the username in UPN format (user@domain). I have also tried entering the domain and username separately. I still get the parameter error.
Has anyone successfully used this function and any sample code to share?

dim w as new WindowsProcessMBS
dim a as Integer
dim AppPathStr, AppName as string


w.ApplicationName = AppPathStr + “” + AppName

if not then
print "Launch Error: "+w.LastErrorMessage
end if