Language switcher doesn't appear in menu

Hi,
I have the Catch Box theme, a custom menu and I put “display language switcher in menu” in the Polylang settings, but it doesn’t work. I search for this issue in the doc and I found the link to a thread in the forums, but it doesn’t work as I don’t have a navigation or library php or event “return theme_get_list_menu($args)” in the header.php. I don’t know a lot about code so maybe I’m looking at the wrong place… I switched theme but I can’t find it neither.
Thanks a lot for your help

my blog: leahudson.com

http://wordpress.org/extend/plugins/polylang/