Factory fault shoes

I purchased shoes sometime in April 2023 which I was planning on wearing on Holiday in December, I have recently tried both shoes on, one has a fault and they refuse they to take it back, the shoes are not in a wearable/resale state as there is a fault with them and they will not take them back because I waited too long, how was I supposed to know they have a fault? What am I supposed to do with shoes that have a factory fault?