How to recalculate the cart after applying the cart rules coupon?

Question

1C-Bitrix

Hello!
There is a slightly customized sale.order.ajax. Also, in his template, a basket is displayed to the heap. There is also a coupon entry field. The problem is that when using a product discount coupon (via CCatalogDiscountCoupon::SetCoupon() ) everything works fine. But with a coupon, there are no basket rules.
The component has the following code:

$couponsDB = CCatalogDiscountCoupon::GetList(array("ID" => "ASC"), array("COUPON" => $_POST['COUPON'], "ACTIVE" => "Y"));

                if($couponItem = $couponsDB->Fetch()) {
                    CCatalogDiscountCoupon::SetCoupon($couponItem['COUPON']);
                    $arResult['DISCOUNT_COUPON'] = $couponItem['COUPON'];
                } else {
                    CCatalogDiscountCoupon::ClearCoupon();
                }

in $_POST['COUPON'] - the coupon code arrives correctly, but the CCatalogDiscountCoupon::GetList() selection is empty.
Tried to test without fetch:

CCatalogDiscountCoupon::SetCoupon($_POST['COUPON'])

- the method returns 1, then I pass it, but further along the code in the CSaleOrder::DoCalculateOrder method , automatic recalculation still does not occur. When applying the coupon in the admin panel - everything is fine. In general, there is a strong feeling that I'm doing something wrong, but I can't figure out what :) $arResult['DISCOUNT_COUPON'] = $_POST['COUPON'];