"Mobile version of…" not showing

Hello there, as requested by Dan, I’m contacting you here for support. I’ve bought the Mobile Smart Pro plugin mostly for being able of choose a different wordpress menu for mobile versions. But in the theme 3clicks (which has wp_nav_menus registered), the “mobile version of…” is not showing.
What should I look for in the theme for fixing this?
Thx in advance,
Sardinha.

https://www.ads-software.com/plugins/mobile-smart/