Sub CPT taxonomy 404 page - url-rewriting

Question

I have a problem with my sub taxonomies.
my-cpt/chapitres archive is working. I made a redirection to a page
from the tax-template.
my-cpt/chapitres/sub-term --> 404
my-cpt/chapitres/sub-term/post --> working
This is my code :
cpt
function custom_cpt() {
$labels = array(
'name' => __( 'Mon cpt' ),
'singular_name' => __( 'Mon cpt'),
'menu_name' => __( 'Mon cpt'),
'parent_item_colon' => __( 'Parent Mon cpt'),
// Paramétrages
'all_items' => __( 'Mon cpt'),
'view_item' => __( 'Voir'),
'add_new_item' => __( 'Ajouter du contenu'),
'add_new' => __( 'Ajout contenu'),
'edit_item' => __( 'Modifier'),
'update_item' => __( 'Mettre à jour'),
'search_items' => __( 'Rechercher'),
'not_found' => __( 'Non trouvé'),
'not_found_in_trash' => __( 'Non trouvé dans la corbeille'),
);
$args = array(
'label' => __( 'my-cpt'), // label
'description' => __( 'Mon cpt'),
'labels' => $labels,
'menu_icon' => 'dashicons-book-alt',
'supports' => array( 'title', 'editor', 'excerpt', 'thumbnail'),
'public' => true,
'hierarchical' => false,
'rewrite' => array('slug' => 'my-cpt/%chapitres%', 'with_front' => false),
'show_in_rest' => true,
'show_ui' => true,
'show_in_menu' => true,
'show_in_nav_menus' => true,
'show_in_admin_bar' => true,
'has_archive' => false,
'can_export' => true,
'query_var' => true,
'exclude_from_search' => false,
'publicly_queryable' => true,
'capability_type' => 'post',
'menu_position' => 5,
);
register_post_type( 'my-cpt', $args );
}
add_action( 'init', 'custom_cpt', 0 );
Taxonomy:
add_action( 'init', 'custom_cpt_taxonomies', 0 );
function custom_cpt_taxonomies() {
$labels = array(
'name' => _x( 'Chapitres', 'taxonomy general name' ),
'singular_name' => _x( 'Chapitre', 'taxonomy singular name' ),
'search_items' => __( 'Rechercher un chapitre' ),
'all_items' => __( 'Tous les chapitres' ),
'parent_item' => __( 'Chapitres Parents' ),
'parent_item_colon' => __( 'Chapitre Parent:' ),
'edit_item' => __( 'Modifier' ),
'update_item' => __( 'Mettre à jour' ),
'add_new_item' => __( 'Ajouter un chapitre' ),
'new_item_name' => __( 'Nouveau chapitre' ),
'menu_name' => __( 'Chapitres' ),
'has_archive' => false,
);
register_taxonomy('chapitres',array('my-cpt'), array(
"labels" => $labels,
"hierarchical" => true,
"public" => true,
"show_ui" => true,
"show_admin_column" => true,
"show_in_nav_menus" => true,
"show_tagcloud" => true,
"show_in_rest" => true,
'rewrite' => array('hierarchical' => true, 'with_front' => false ),
));
}
I found this for the rewrite rules
function rewrite_permalink_cpt($link, $post){
if ($post->post_type != 'my-cpt')
return $link;
if ($cats = get_the_terms($post->ID, 'chapitres')){
$link = str_replace('%chapitres%', get_taxonomy_parents(array_pop($cats)->term_id, 'chapitres', false, '/', true), $link);
}
return $link;
}
add_filter('post_type_link', 'rewrite_permalink_cpt', 10, 2);
add_filter('rewrite_rules_array', 'rewrite_rules_permalink_cpt');
function rewrite_rules_permalink_cpt($rules){
$cpt = array();
$cpt['my-cpt/(.+)/(.+)/(.+)/(.+)/?$'] = 'index.php?my-cpt=$matches[4]';
$newRules['my-cpt/(.+)/(.+)/?$'] = 'index.php?my-cpt=$matches[1]';
return array_merge($cpt, $rules);
}
function get_taxonomy_parents($id, $taxonomy, $link = false, $separator = '/', $nicename = false, $visited = array()) {
$chain = '';
$parentref = get_term($id, $taxonomy);
$parent = &$parentref;
if (is_wp_error($parent)) {
return $parent;
}
if ($nicename)
$name = $parent->slug;
else
$name = $parent->name;
if($parent!=0){
if ($parent->parent && ($parent->parent != $parent->term_id) && !in_array($parent->parent, $visited)) {
$visited[] = $parent->parent;
$chain .= get_taxonomy_parents($parent -> parent, $taxonomy, $link, $nicename, $visited);
$chain .= "/";
}
if ($link) {
// nothing, can't get this working :(
} else
$chain .= $name;
return $chain;
}
}
I think the problem is come from the rewrite rules, but I don't know what is wrong...
It would be appreciate if someone has an idea