why category__and is not working.

query_posts ( array( ‘post_type’ => ‘ait-dir-item’, ‘category__and’ => array(6,39), ‘posts_per_page’ => 12, ‘orderby’ => ‘title’, ‘order’ => ‘DESC’ ) );

I am trying to display (get posts) from 2 categories. but when I put “category__and”
It shows nothing.

any problem?

[continue with https://www.ads-software.com/support/topic/get-posts-from-2-categories-and-different-taxonomies?replies=9 ]