Hello,
Sorry to hear you are having issues. Please try purge and reinstall steps as mentioned here: [link]. Just make sure to redownload the latest version from your account. Reboot after the purged. Reinstall, and Reboot again after the installation. Retest it. Report back here.

Basj,
Stardock Community Assistant.

And why did you create a new thread?

BTW, can you install them when you download directly from Wincustomize.com? https://www.wincustomize.com/explore/curtains

Thank you,

Basj,
Stardock Community Assistant

It seems to be an issue with permissions. I unpacked the style and tried to copy it into the .../Documents/Stardock/Curtains folder, but I get a strange error message like "the element does not exist".... All the other styles are there and I can switch between the ones already installed. 

I uninstalled again, purged, deleted the styles-folder with Lockhunter, reinstalled, and now it works again. 

Sadly, it went back to not working after the next reboot. At first, when it worked, there was only the original Win 10 style present in the local tab. After a reboot, under the local tab there were around 15 styles, and now again I can't install any new ones any more. 

Also, when I have the "Eleven Dark" style active, none of the changes to the startmenu with Start11 work: startbutton, background of menu etc. So not only concerning centered icons on the taskbar they are not compatible at the moment, but also concerning those elements. 

If it wasn't set to Curtains, I suppose Curtains would not open when clicking on such file. Also, in the context menu, it says "Install Curtains style". Something gets messed up with the permissions, even if it initially works, when a default selection (?) of styles gets installed locally. Or a relict in the registry, that leads to custom styles I loaded earlier being reinstalled? But shouldn't registry entries of any kind be purged after selecting "delete all settings" while uninstalling or at least with the batchfile? I can make no sense out of what is happening.