a to z claim appeal denied

I had a a to z claim denied, customer said never got package wven though usps showed delivered. I used Amazon buy shipping label and it was protected. I shipped on time, usps scanned package at 11am on 1/21. Amazon said ship by 1/21 11:59pm. Amazon email said i didn’t ship on time so they denied claim amd I wasn’t covered when it should be covered 100%

Anyone experience this?