ehsan20

I found it. Hooraaaa !

I replaced:

                $arms = array(
                    'post_type' => 'product',
                    'posts_per_page' => '9',
                    'order' => 'DESC',
                    'post_status' => 'publish',
                    'post__not_in' => array($post->ID),
                    'tax_query' => array(
                        array(
                            'taxonomy' => 'product_cat',
                            'terms' => $trmarray,
                        ),
                    )
                );

with:

global $product;
$crosssell_ids = $product->get_cross_sell_ids();

                $arms = array(
                    'post_type' => 'product',
                    'posts_per_page' => '9',
                    'post__in' => $crosssell_ids,
                    'order' => 'DESC',
                    'post_status' => 'publish'
                    
                );

and it did the trick.