valid for these styles:
Flavius is a style that has some depencies which need to be installed with the style - otherwise the style will not work correctly.
You imported one or more of the Flavius styles and after activating them in your WoltLab Suite you get an error that's something like Could not compile SCSS: Undefined variable $wcf_option_flavius_settings
You imported the style only but didn't install the complete package.
Delete the style(s) you've imported the way described above. Then install the complete style package from Elevenfour's package server. This way all dependencies are loaded correctly.