Yemeksepeti New User Coupon Cannot Be Used on Orders

I registered as a new user on Yemeksepeti and, according to the campaign, it was stated that new users would receive a ₺300 discount coupon for their first order. Today I tried to benefit from this coupon but I could not use it in any way. When I tried to add the ₺300 coupon to the “My Coupons” section, the application displayed a message saying that the coupon had been added and that I could see it there. However, no coupon appeared in my coupon list on the order screen. When I tried to use the coupon during the ordering process, I received an error stating that the coupon could not be used. I also tried to reach Yemeksepeti customer service about this issue, but I could not find any live support or a clear communication channel to resolve the problem, so I was left without any help. I request that the ₺300 new user discount coupon, which was promised but could not be used due to this error, be defined to my account correctly and that I be allowed to use it on my order.