Coffee Voucher Fail!

How disappointed was I last night. I went to redeem the free little coffee listed on the app as a big promotion just to be told sorry it does not work and xpired? How is this possible as it stated on the voucher valid till 27th August 2024. The guy just said nothing he can do about it and went on with the next customer. 3 other people were also turned down. What an epic fail I complained on Facebook but even on there the response is a non existent as the coffee.