Temu refuses to refund me

My parcel was lost in transit in may 2024, I received a lost letter from buffalo logistics on the 01 April 2025. I sent the letter that I’ve waited for a long time to request my refund from Temu, but they refused to refund me since they claim that the app has marked the parcel received. I feel being treated unfairly since they said I must send evidence from the courier company. I did that but still no refund. I need help on how to take further steps because I’ve worked so hard to get my money, so they can’t just enjoy life on my expense