publish new post via the front-end and adding to it a custom taxonomy term

I have a form which is adding new posts via the front-end using the function wp_insert_post, my problem is when i'm trying to attach the new post to a custom taxonomy term.

this is my code:

$new_post = array(
    'post_title'    => $title,
    'post_content'  => $description,
    'post_status'   => 'pending',
    'post_type' => 'post'
);
$pid = wp_insert_post($new_post);
wp_set_object_terms($pid, array('men2', 'women'), 'group');

my custom taxonomy is hirarrchial (like categories).

the problem is that the wp_set_object_terms doesn't add this to the new post.

Any suggestion?