Well, this is another "phenomenon" - in the menu item, if I specify Filter Parent Category ID, there will be nothing displayed.
In my case, Nature Gallery has no Filter Parent Category ID specified and you can see various categories, including "Landscapes" (now with pictures for you). This "Landscapes" category has ID945. If I write 945 in the Filter Parent Category ID menu option, the result is empty page.
The Nature menu has no ID specified, and everything is displayed. If I change it and write any id in the Filter Parent Category ID of the menu, everything is gone.
Thank you in advance for help!