If you mean Academi from the plugins database, it looks like there is a problem with the order of the css sheets in the config file
custom.css is actually listed first, which means then that any settings in theme.css will continue to overwrite anything added to the customcss setting.
You may need to change this yourself on your version or contact the developer to fix it.
$THEME->sheets = array('custom','theme','font-awesome.min');
$THEME->sheets = array('theme','font-awesome.min','custom');
Personally, I'd probably put the font-awesome one first as well as that appears to be the upstream file from font-awesome and I tend to put those before anything created for the theme itself so that the theme.css would overwrite the upstream ones without changing them, if that should become necessary - makes for easier upgrading if you ever have to change the upstream file (IMHO)