SeatGeek Promo Code Not Working At Checkout, Why?

I attempted to use a promo code I obtained from one of your partner things to purchase concert tickets the other day (May 15th). I opened the app, went to "Me," and entered the code precisely as instructed on your website and in the app but the code wouldn't work when I tried to use it at checkout! Before purchasing the tickets, made sure I was logged in and that the code was valid. At first, it appeared to accept the code; however, when I went to make the payment, it was absent. the person I spoke with after an eternity on hold was completely ineffective, only thing they said was to try entering the code again, which I've obviously done many times before. not useful.