my birthday promo code doesn't work

I was sent a discount code of 28000₩ for my birthday. This code is valid until  october 31th and on purchases of at least 129999₩, it must be entered at checkout, but when I go to enter it it says that it is not valid. What should I do? help. The sentence in red that tells me is: "We are sorry, it is not possible to apply this promotion", the item in question is a razer basilisk v3 pro 35k.