Import Module Fn_Add_Product_To_Cart Problem

i am makin and import module but doesnt apply promotions if product have promotion ( notification show but promoted products doenst there)

    $product_data['price'] = $price;
    $product_data['stored_price'] = 'Y';
    $product_data['amount'] = $product->quantity;

fn_add_product_to_cart(array($product_id => $product_data), $cart, $customer_auth);

fn_calculate_cart_content($cart, $customer_auth, ‘A’, true, ‘F’, true);

if ($res = fn_place_order($cart, $customer_auth)) {
list($order_id) = $res;

i am addign with this way. whats the problem ?

promotion applied notification is show. but eg: buy one get x promotion products doesnt include cart