Wp_User_Query not sorting by meta key

you can try this code

 $args = array(
            'meta_query' => array(
                    array(
                        'key'     => 'score',
                        'value'   => 0,
                        'compare' => '>',
                        'type'    => 'numeric'
                    )
            ),
            'orderby' => 'meta_value_num',
            'number' => 20
 );

 $suggested_user_query = new WP_User_Query( $args );
 $users = $suggested_user_query->get_results();
 echo '<div id="user_suggest">';
            echo '<ul>';
                foreach ($users as $user) {
                 // get all the user's data
                 $user_info = get_userdata($user->ID);
                 echo '<li>';
                echo '<h3>'.bp_core_get_user_displayname( $user->ID ).'</h3>';
                $score = get_user_meta( $user->ID, 'score', true );
                 echo $score;
                 echo '</li>';
                }
            echo '</ul>';     
 echo '</div>';

For more information you can check this link
https://codex.wordpress.org/Class_Reference/WP_User_Query