Custom CSS

I have a weird problem, which I think has something to do with Virtue theme.
I have qtranslate x installed and the site runs in three languages. Temporary I would like to hide one language from the language swithcer, which is a menu in the topbar.
The author of the plugin told me to put this in my theme css:

.qtranxs-lang-menu-item-ru{
	display: none !important;
}

I tried to add this through appereance – edit – stylesheet.css with no luck, then through theme settings advanced css, still nothing.
It made no change in Virtue, but it did exactly what I wanted in Twentyfourteen. So my guess the problem is here in Vurtue. Any solutions would be greatly appreciated. Thank you!