Invoke-VMScript with the ScriptType bat runs your command with a cmd.exe line.
If the application you are calling requires a GUI, it will not work.
I don't know that application, but since it is described as a GUI Test tool, I'm afraid it will not work via Invoke-VMScript.
Is there a way to call a GUI test remotly via PowerCLI scripting?
Just to be clear:
The Invoke-VMScript in ny script calls a batch file.
The batch file runs the GUI test.
Not that I know off.
There is no interactive session, so you can't start a GUI session I'm afraid.