Shipment not received despite UPS delivery confirmation!

This shipment was made in September, 2022, and UPS gave us a confirmation that Amazon received the shipment at their dock but they say they didn’t get it. What can we do?

When we receive shipments with quantity discrepancies, we automatically initiate an investigation on your behalf for the items in your shipment. As part of this investigation, we perform a second, physical count to reconfirm the quantity of the items received. Items are marked “Investigation Completed–shipment contents counted and confirmed” when we have completed the review. We have completed an additional check in response to your request. We have no record of receiving the units in question.

Thanks, Bill