I don't have Invoices and Need to Provide POA to Amazon on Product Authenticity Complaints

Hello, I hope you’re all doing good,

I received a Product authenticity complaint because a Customer has reached Amazon saying that the product I sent was Inauthentic, as I have sold 850+ Units of this product and never received any complaint from buyer. But now 1 customer complained and Amazon deactivated my listing. And Amazon is asking me for Invoices. I admit that I made a mistake not reading Amazon policy and I didn’t know that Amazon can ask me for Invoices. I purchased this product from a authentic Supplier but the they did not give me Invoices of my purchase they just gave me receipts I bought this product physically and was shipping it by myself, and I contacted supplier many times but they say we do not provide invoices for physical orders, I requested them but they are not helping me. I contacted Amazon by using call me now button they told me that now I only have 1 option to submit a POA then I can get my listing activated and then I provided my POA to Amazon but they did not accepted Now what should I do Can Anyone Guide What type of POA should I submit.