Error when loading new global theme in KDE


I’m a newbie in nixos and I need help:I am trying to download new global themes in KDE and I always get an error message like this:

Installation failed .... Cannot install dependency of /tmp/kfcxZj-Bonny-Global.tar.gz:: << kns: //colorschemes.knsrc/> >

I think I have to do something first but what?

I think i cannot be more clear:

Appearance → global theme → download new global theme → Ans always same error message…

Known issue - see