Extension "PDF Export Collection Application" is missing pages in exported document


I wanted to export a part of my documentation, which is hosted on XWiki 11.10.4 LTS.

So I’ve installed the extension “PDF Export Collection Application” by Paul Cojan:

Sadly it does not work as intended. Creating a collection works fine but when exporting, the resulting pdf is missing the articles in the collection.
The articles I’ve added for test just contain some lorem ipsum an an image.

Does anyone know how to resolve this or which error logs to check?

Thank you very much in advance!