I have have the same problem. I have 3 categories and two of them are showing content and one of them is just empty? I tried your advices from above, but it didn't change. hmmm?
Btw. really nice theme :v:
I've got it!:yum:
For others who have the same problem:
I´ve got the tip from a friend to click on "Ansicht anpassen" and to tick on "project thumbnail"
Now I can add a featured image :hand: :dancer:
I try to add a new project, but there is no window for adding a featured image/ thumbnail, as shown on your tutorial video. Any idea what is wrong?