Koçtaş Discount Coupon Scam

I used to think Koçtaş was advantageous, but unfortunately, they're not reliable. I couldn't use two personalized discount coupons. When I add the product I want to purchase to my cart and enter the discount coupon code, it says, "There are no items in your cart eligible for this discount coupon" (as shown in the image, it says this for all products). I called the support line about this, and they said they would process my complaint and request, but it's been 10 days with no response, and now the discount coupon has expired. All relevant images are attached. The discount coupons were for ₺500 + ₺200 off.