Amazon Rejects the Return of My Order Without Any Reason

I purchased six vitamin supplements from Amazon for my cousin, who was leaving abroad in two days. The delivery time was supposed to be one day, but the items were not delivered on time. My cousin left the day after the scheduled delivery, and the order arrived two hours later. Since I no longer needed them, I tried to return the items, but I received a message saying they were not eligible for return, even though the return page stated they could be returned within 30 days. There was no customer service available to contact. I had never faced such issues with Amazon before and always preferred it for its reliability, but this last order was a real disappointment for me.