After the last update, MCC stopped working due to a bugged yad version (7.0).
A possible workaround is to install a newer version of yad (7.1) from the unstable branch
Do the following commands:
sudo pacman-mirrors -B unstable --api sudo pacman -Syy sudo pacman -S yad sudo pacman-mirrors -B stable --api sudo pacman -Syy
Anyway there is still access to settings from for example Right SidePanel super + TAB