Cannot add custom taxonomy to specific menu

I’m trying to add a custom taxonomy to a menu, but for some reason it won’t show.

This is the custom post type that I want use to associate the taxonomy:

$  labels = array(     'name' => 'Esperienza',     'singular_name' => 'Esperienza',     'menu_name' => 'Esperienza',     'all_items' => 'Esperienza',     'add_new' => 'Aggiungi nuovo',     'add_new_item' => 'Aggiungi nuova Esperienza',     'edit' => 'Modifica',     'edit_item' => 'Modifica Esperienza',     'new_item' => 'Aggiungi nuova Esperienza',     'view' => 'Visualizza Esperienza',     'view_item' => 'Visualizza Esperienza',     'search_items' => 'Cerca Esperienza',     'not_found' => 'Nessun Esperienza trovata',     'not_found_in_trash' => 'Nessun Esperienza trovata',     'parent' => 'Esperienza genitore',     'filter_items_list'     => 'Esperienza $  s',     'items_list_navigation' => 'Navigazione',     'items_list'            => 'Lista Esperienza',     'view items'    =>    'Visualizza Esperienza',     'attributes'    =>    'Attributi Esperienza' );  $  args = array(     'labels'  => $  labels,     'public' => true,     'publicly_queryable' => true,     'show_ui' => true,     'query_var' => true,     'rewrite' => array('slug' => 'st_experiences'),     'has_archive' => true,     'hierarchical' => false,     'menu_position' => 0,     'show_in_menu' => 'edit.php?post_type=st_tours',     'supports' => array('title', 'editor', 'author', 'thumbnail', 'excerpt', 'comments'),     'taxonomies' => array('st_experience_categories') );  register_post_type('st_experiences', $  args); 

and this is the custom taxonomy:

function experience_category_post_type() {     $  labels = [         'name' => __('Categorie esperienze', 'traveler'),         'singular_name' => __('Categorie esperienze', 'traveler'),         'search_items' => __('Search Categorie esperienze', 'traveler'),         'popular_items' => __('Popular Categorie esperienze', 'traveler'),         'all_items' => __('All Categorie esperienze', 'traveler'),         'parent_item' => null,         'parent_item_colon' => null,         'edit_item' => __('Edit Categorie esperienze', 'traveler'),         'update_item' => __('Update Categorie esperienze', 'traveler'),         'add_new_item' => __('Add New Categorie esperienze', 'traveler'),         'new_item_name' => __('New Experience Type Name', 'traveler'),         'separate_items_with_commas' => __('Separate Categorie esperienze with commas', 'traveler'),         'add_or_remove_items' => __('Add or remove Categorie esperienze', 'traveler'),         'choose_from_most_used' => __('Choose from the most used Categorie esperienze', 'traveler'),         'not_found' => __('No Categorie esperienze.', 'traveler'),         'menu_name' => __('Categorie Esperienze', 'traveler'),     ];      register_taxonomy('st_experience_categories', array('st_experiences'), array(         'labels' => $  labels,         'show_ui' => true,         'show_admin_column' => true,         'query_var' => true,         'rewrite' => array('slug' => 'st_experience_categories'),         'show_in_menu' => 'edit.php?post_type=st_tours',         'show_in_nav_menus' => true,         'hierarchical' => true     )); }  add_action('init', 'experience_category_post_type'); 

when I visit my custom post I correctly see the taxonomy on the right menu:

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but on the left side menu I can’t get displayed:

enter image description here

what I did wrong?