Looks like others have already determined what the issue is, but I'm having the same problem as well with Variety changing wallpapers with the new version (4.11) of KDE. Symptoms are same as described above: no automatic or manual switching of the wallpaper by the Variety app. Wallpaper changes are only possible by opening desktop settings and re-applying the kde-wallpaper image.
Looks like others have already determined what the issue is, but I'm having the same problem as well with Variety changing wallpapers with the new version (4.11) of KDE. Symptoms are same as described above: no automatic or manual switching of the wallpaper by the Variety app. Wallpaper changes are only possible by opening desktop settings and re-applying the kde-wallpaper image.