Can't create object for multi instance when using GetObject("myconfig1")

Hello,

I have the Indesign Server CS6 Multi Instance. I create an instance using the InDesign Server Windows Service:
Port: 12000
Args: -configuration myconfig1

Now I tried in Visual Basic: GetObject("myconfig1")
Then I get a can't create ActiveX component exception.

Notes:
The service "InDesignServerService x64" is running.
The InDesign Server instance was started.
I can access the instance via SOAP: http://localhost:12000/

Why can I not create the object in Visual Basic?

Thank you for help!

Harald