OfferUp complaint: Item damaged in shipping

My complaint:

I was long my denon heos amp to a buyer in Florida. I shipped item and buyer notified me item was damaged during shipping. Item was in full working order. Now he want refund and all I get back is a damaged item

Suggested solution:

I should be given reimbursement or my damaged item or a replacement for it. They made the label and should have insurance at usps. But they forced me to ship through them. So insurance is there responsibility they say that we are given the same protection as buyers