wp_insert_term() doesnt insert a term

Thanks to Milo who asked an important question: Where is this code?

I put it below where ive have registered the taxonomy and then it worked:

function register_taxonomy() {
       $labels = array(...);
       $args = array(...);

       register_taxonomy( 'ncategory', null, $args );

        $parent_term = term_exists( 'Gender', 'ncategory' ); // array is returned if taxonomy is given
        $parent_term_id = $parent_term['term_id']; // get numeric term id

//echo $parent_term_id;

  $ret = wp_insert_term(
 'Male',
  'ncategory',
     array(
        'description'=> '',
    'slug' => '',
    'parent'=> $parent_term_id
  )
);

   echo is_wp_error($ret);

}