Try use meta_value
instead of meta_value_num
.
$args = array(
'post_type' => 'product',
'posts_per_page' => 20,
'orderby' => 'meta_value',
'meta_key' => 'pa_review_date',
);
Try use meta_value
instead of meta_value_num
.
$args = array(
'post_type' => 'product',
'posts_per_page' => 20,
'orderby' => 'meta_value',
'meta_key' => 'pa_review_date',
);