Not working with Customizr theme?

Trying to get JC Submenu to work on my site https://peterhjalmarsson.hopto.org/donostia.se/ (development site). I want to automatically populate the menu “Artiklar-JCTest”, and have followed the instructions to the letter. However, it does not populate at all. In the documentation, you talk about “custom walkers”, and I have no idea what that is or if my theme (Customizr) is using it.
I have tried using the functions.php code from your doucmentation

add_filter('jcs/enable_public_walker', 'jc_disable_public_walker');
function jc_disable_public_walker($default){
    return false;
}

but that does not help at all. For the time being, I’ve left it in there, if you are looking at the dev site.

Help?

https://www.ads-software.com/plugins/jc-submenu/