FBA Discrepancy

Hello!

Last month we sent one box with 4 items in it to FBA, which only 1 was received. Our distributior has states multiple times they have camera footage of all 4 items being placed in the box, and the UPS weight matches exactly to what it should be. We have asked Amazon multiple times to investigate this, providing an invoice with 4 serial numbers attached, and all times they come back saying they have recounted and confirmed there was only 1 item.

Finally they sent us a long message back stating they have investigated this multiple times, searched their network and nothing had been found nor any proof we actually sent 4 items. They also said this matter is closed and any additional appeals will not be considered.

Now we are in a spot of how to get our money back as our distributor is unwilling to refund based on their investigation, and Amazon is also not willing to refund us. Does anyone have any advice on how to proceed?