After a recent system update, I encountered an issue when attempting to use the Alt-Tab shortcut twice to bring up the task selector. A notification through kdialog displayed an error message, which reads: "The Window Switcher installation is broken, resources are missing. Contact your distribution about this." It's worth mentioning that this issue has arisen on my Artix system, which hadn't undergone any updates for approximately a month prior to this incident.
You're missing a package. Probably a kde plugin that is not in the main kde meta but in kde plugins. I assume its a kwin plugin.
1. Remove files in ~/.cache
2. Do pacman Scc
3. Do pacman Syyu
4. Locate the missing kde kwin plugin and install it.