Custom posts not showing in Category-tree

I’ve created a custom post type (called “Artikel” – “Article” in english) and a corresponding template for single-post viewing with the Pods plugin and these seem to work perfectly. But when I create a category tree with WP-dTree it wont show the posts from this new custom type even though they are marked with the right category/categories. The post count in the parenthesis next to the category name in the tree counts the posts of the custom type, but they are not listed inside the category when it is expanded. The tree is, however, perfectly capable of listing the regular posts in the right categories – just not the custom ones.

I’ve made a category called “Artikel” (ID: 5) and child-categories underneath it and marked all the posts of the custom type with one or more of these categories. I’ve put “Show descendants of:” to “Artikel (ID: 5)” and “Only *direct* children of” to “Don’t filter on parents”

The Archives-tree is able to show the custom posts correctly, but I need a tree-menu that lists categories, not months of publishing, and then the post titles within these categories.

Am I doing something wrong?