My own plugin application is working fine from inside a Previewer component in the Windows and WebGUI and also in the Universal GUI when the application in opened in the browser on the server that hosts IIS.

But when I start the application from another PC the previewer remains empty. What can be the reason?

The plugin application is running from the same IIS instance as Indicium and Universal
IIS:

The previewer should show https://test.xxxxx.nl/smartextender
What can be the problem and how can it be solved?