Order WP_Query by vafpress meta

I'm trying to order a custom-post-type WP_Query by a custom vafpress metabox:

$args_voyages = array(
    'post_type' => 'voyage',
    'order' => 'ASC',
    'orderby' => 'meta_value_num',
    'meta_key' => vp_metabox('meta_voyage_features.meta_voyage_features_price'),
    'rewrite' => false,
    'meta_query' => array(
        array(
            'key' => '_thumbnail_id',
            'compare' => 'EXISTS'
        ),
    ),
    'tax_query' => array(
        'relation' => 'AND',
        $array_current_destination,
        $array_current_zone,
    ),
);
$voyages = new WP_Query($args_voyages);

The WP_Query is not returning any result. I tried this options too, with no results:

'meta_key' => 'meta_voyage_features.meta_voyage_features_price'

and

'meta_key' => 'meta_voyage_features_price'

Can anyone help me?

Thankyou very much!