Commerce 11.8.2

Currently using out of the box promotions. We have an "Apply Promotion Code" input at the basket level.

Looking at the code in Quicksilver we are doing this:

            var cart = _orderRepository.LoadOrCreateCart(_contactId(), Basket.DefaultName, _currentMarket);
            
            if (cart == null)
            {
                return _commandResultFactory.Create(CreateValidationResult("Error Creating Basket"));
            }

            var couponCodes = cart.GetFirstForm().CouponCodes;
            if (couponCodes.Contains(command.Code))
            {
                return _commandResultFactory.Create(CreateValidationResult("Error Adding Promo Code to Basket"));
            }

            couponCodes.Add(command.Code);
            var rewardDescriptions = cart.ApplyDiscounts(_promotionEngine, new PromotionEngineSettings());
            var appliedCoupons = rewardDescriptions.Where(r => r.Status == FulfillmentStatus.Fulfilled).Select(c => c.Promotion.Coupon.Code);
            var couponApplied = false;

                couponApplied = appliedCoupons.Any(c => c.Equals(command.Code, StringComparison.OrdinalIgnoreCase));

            if (!couponApplied)
            {
                return _commandResultFactory.Create(CreateValidationResult("Failed to apply promotion"));
            }

            var orderReference = _orderRepository.Save(cart);

We get no exceptions when doing this and it runs through, but what we're not seeing is any change in lineitems price or total cart price. I can't see what is different between what we're doing and whats in the reference project.

Can anyone shed any light on how to apply promotions on a cart and show the relevent discounted price.