As a seller, it's your responsibility to ensure that the shipment is delivered to the buyer.
As long as tracking information shows delivery confirmation to the buyer's address, you are not required to take any action. You should advise the buyer to file a police report and/or stolen package claim with their local courier.
In some cases, the package may have been erroneously marked as delivered earlier than the actual delivery date. In others, the package may have been stolen if a signature was not required. Regardless, the buyer is responsible for locating the package after it has been marked as delivered.
However, if tracking information is inconclusive for an extended period of time, you should file a lost/stolen package claim with your courier so they can put out a search for it. If the courier is unable to locate or deliver the package, the buyer is entitled to a full refund for this sale.
Please note that seller protection does not apply for items that are lost or damaged in transit. You must have tracking information showing confirmed delivery to the buyer's shipping address in order to be eligible for seller protection coverage.
Please be sure to contact our support team directly if you need any assistance following the steps above.