Polylang language switch does not show

When we did the recent update to the newest wordpress-version on the blog http://www.wellwishes.nl, something went wrong in the way the Polylang plugin shows menu item in two languages. It features both dutch and english in a menu switcher, and the Journalzone-theme that we use doesn’t switch language anymore. This theme does not seem to have the wp_nav_meucode, so what to do?