When installing WPML 3.6.0, if one of the layouts you created with the Toolset Layout plugin uses the Language Switcher widget, this widget might not be rendered.
The next version of Layouts will provide improvements in Widget's handling, which should solve this issue.
For the time being, in order for the language switcher to be rendered, you must use one of the following options:
1. Replace the widget with a text area and use one of the following shortcodes:
[wpml_language_selector_widget]: it can be customized in WPML -> Languages -> Custom language switchers
[wpml_language_selector_footer]: it can be customized in WPML -> Languages -> Footer language switcher
2. Add a sidebar in your theme, and place there the Language Switcher widget.
do_action(‘wpml_add_language_selector’); to display a custom language switcher as explained in Displaying WPML’s language switchers in custom locations