Complaint about Buffalo logistics

I bought 2 packages from Shein and they were supposed to be delivered to me by now and I did not receive them yet, but when I trace my packages it reflects as delivered on 23rd april 2023 which was on Sunday and as far as I know they said they don't work on weekends.when I enquire with Buffalo logistics they keep on telling me that they are still investigating, I feel disappointed by the company and feel like they are not taking care of their customers and I'm always phone and keep getting the same answer of them still investigating, please help Peter.