Amazon will not accept their own order invoices as proof of authenticity. You have no clear ‘Chain of Custody’ from the manufacturer to you. Maybe these were returns and maybe swapped with counterfeits. Unless you can show an invoice direct from the manufacturer or their authorized distributor, you cannot win an authenticity dispute.
Also, many manufacturers have updated there warranty policies to only be valid if purchased from authorized distributors/retailers. As a result of this, your item, although sealed and ‘New’ condition, would not meet the requirements by Amazon to sell as ‘New’ – Amazon says that to be ‘New’, the full manufacturer warranty is required.
So, if you begin to sell again, and you are not sourcing through reseller agreements with the manufacturer or IP owner, you will likely find more of these complaints which will result in a permanent suspension of your seller account. Please do your research on the brand, its warranty policies and work to source direct – it will be much cheaper for you with higher margins than buying from a retailer, even if on sale.
Search these forums for the brand as well. There are hundreds of brands that self-monitor and report infringement claims to Amazon.
And… Never rely on Amazon telling you if you can sell or not. Amazon is a retail platform – the expect sellers to know what their business can and cannot sell. So larger brands have worked with Amazon to restrict listings, but not every brand does.