Why did A-Z Claims deny my claim without giving me a reason?

I am confused, it has been 4 months since the purchase. The customer suddenly filed an A to Z claim claiming that he did not receive part of the product, I appealed to Amazon, but it was rejected every time even though we have all the receipts.

They did not tell us the reason for the rejection, and the response we got every time was "Amazon insisted on his decision even though they understood my position."

Why is this happening, we need a reason, because we have shipped everything within a week of the customer's order. And the customer claimed that he did not receive some parts, but Amazon refunded him all the money, the amount is so large.

We provided all the carrier information and logistics tracking number, and the receipt, but it still did not work. It has been 4 months, and the carrier can't find the logistics at all. I called the carrier many times, and they helped us find the receipt at that time, but this did not work for Amazon, they always gave me the same response, rejecting my appeal. What should I do, who can help me!

In addition, how can I get my money back? This is a completely wrong refund, he just claimed that some parts were not received, but Amazon refunded all of them. And the parts he claimed he didn't receive were also received, why didn't our evidence do anything?

Please help me, I need a fair outcome and need my money back!

I opened a case and submitted the information, case ID: 16368576971, but the response I received was of no use.

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