get_terms() parent, child and grandchild

Question

parent1 - child1 - grandchild1

I need to show child terms of any current term (only direct child) for each term I visit. Works only for the parent (show child1) but not for the child (doesn't show granchild1)

How I can fix this issue? Thank's

$queried_object = get_queried_object();
$cpt = get_post_type( get_the_ID() );
$taxonomy = $queried_object->taxonomy;
$term_id = $queried_object->term_id;

echo 'cpt - '.$cpt;
echo '<br>tax - '.$taxonomy;
echo '<br>term id - '.$term_id;

$customPostTaxonomies = get_object_taxonomies($cpt);
if ( $customPostTaxonomies ) {

     foreach($customPostTaxonomies as $tax) {
         $args = array(
              'orderby' => 'name',
              'hierarchical' => 0,
              'taxonomy' => $tax,
              'field' => 'id',
              'parent'=> $term_id,
              'title_li' => ''
              );
         wp_list_categories( $args );
     }

UPDATE:

Structure:
cpt = corsi
tax = argomenti
tax_term = parent1
tax_term_child = child1
tax_term_child_granchild = grandchild1

Answer 1

Since this is for a taxonomy archive, you can just use get_queried_object() and the parent and depth argument in wp_list_categories():

$term = get_queried_object();
$list = wp_list_categories( array(
    'orderby'  => 'name',
    'taxonomy' => $term->taxonomy,
    'parent'   => $term->term_id,
    'title_li' => '',
    'depth'    => 1,
    'echo'     => false,
));

if ( $list ) {
    echo "<ul>$list</ul>";
} else {
    // Nothing, do something else!
}

Note that wp_list_categories() does not output/return a containing <ul />, so you need to do so yourself (as demonstrated).