Please add taxonomy name in wp_set_post_terms function.
wp_set_post_terms( $id, $prod_cats, 'product_cat' );
Please refer wpcodex wp_set_post_terms
Please add taxonomy name in wp_set_post_terms function.
wp_set_post_terms( $id, $prod_cats, 'product_cat' );
Please refer wpcodex wp_set_post_terms