Agoda Refund Not Issued After Saja Al Madinah Booking Rejected

I made a reservation through Agoda for a standard room at Saja Al Madinah Hotel for 15–17 October and paid $251.13 by credit card. When I arrived at the hotel on 15 October, the reception informed me that the hotel was full and that my reservation was not showing in their system, so they could not give me a room. Neither the hotel nor Agoda offered any alternative solution at that moment, and I was left without the room I had fully paid for. After this incident, I contacted Agoda customer service. They told me they would contact the hotel regarding a refund, but so far I have not received any refund or a clear solution. I request a full refund of the $251.13 I paid for this unused reservation and a clear written explanation of how such a situation occurred despite my confirmed booking.