Negative feedback received because we require signature no help from amazon

The customer gives us negative feedback because we require a signature on a $500 item, UPS tried to deliver the parcel after 3 attempts they had to go to a UPS access point to pick it up he did not want to go pick it up so he gives us a negative feedback,we contact Amazon opened a case Amazon turns around and says contact the customer so we did and the customer wanted to retract the negative feedback but did not know how to we tried explaining after 3 unsuccessful messages we did not want to bother them, Amazon does not want to remove the feedback but we see other sellers were able to have their feedback remove with similar case in this forum but not us just wondering why?

Case ID: 14963167991