Customer Complaint Counterfeit on generic listing!

Can anyone give me a hand with this, I've had a customer complaint of my product being inauthentic/counterfeit, the product is a generic product and has no brand name just "Generic" on amazon.co.uk.

I've submitted the invoice from my supplier for the product and I'm just getting the same message back: We cannot verify your suppliers information, etc.

I've not had any returns on the SKU that even contain the word counterfeit, inauthentic or fake. Same for product reviews, there are no reviews on the SKU that detail that the product is inauthentic.

The product I am selling is identical to the listing on Amazon, I've even got CE + UKCA certfifcation for the stock that I'm selling.

I'm really lost here, thankfully the stock I'd ordered had sold out before the listing was blocked however I'd like to get this sorted as its taking point off of my account health.