I sold an item and buyer contact me and shows never got it. Tracking shows delivered and it was also signed for. Buyer claims they never got or signed for it. When they contacted the post office the were told the post carrier signed for it because of Covid protocol. They dont know where the package its. Buyer feels I should refund them or give a them another item. I did take out ship cover insurance on this. Not sure what to do? Am I responsible for this?