MB_Relationships_API::each_connected does not fetch anything

Hello!
I have created a relationship of “user” to “something”(custom post type) with ID users_to_something.
Then I try to query the relationship between them.

<?php

global $post;
$args = array(
    'post_type'      => 'something',
    'posts_per_page' => -1,
);
MB_Relationships_API::each_connected(
    array(
        'id'       => 'users_to_something',
        'from'     => $test_query->posts, // tried both to/from
        'property' => 'clients',
    )
);

$test_query = new WP_Query( $args );

while ( $test_query->have_posts() ) :
    setup_postdata( $post );
    $test_query->the_post();

    var_dump($post); // the relationship parameter "clients" has nothing inside

    // Display connected pages (not working because there is no relationships found by each_connected)
    foreach ( $post->clients as $p ) :
        // More core here...
    endforeach;

    // Get individually(Working properly.).
    $users = get_users(
        array(
            'relationship' => array(
                'id' => 'users_to_something',
                'to' => get_the_ID(), 
            ),
        )
    );
    foreach ( $users as $user ) {
        echo $user->display_name;
    }

endwhile;

The “each_connected” function seems not working as expected but query separately using “get_user” seems to working.
In this code, is there anything missed in the “each_connected”?