Should I refund this order?

Customer contacted me about their order not moving in UPS shipping the day after I dropped it off with UPS. They ordered 2 day air. The customer contacted me and said “please refund and I’ll buy again” UPS definitely has the item because I dropped it off at the UPS store myself and it was scanned the next day. I do see it hasn’t moved after that though. Should I refund or just let it ride?