Product Authenticity Complaints – Retro Video Games

I recently came across a Product Authenticity Complaint. I primarily receive my inventory from cash or trading. I do go through a process of ensuring everything is authentic so I’m kind of surprised by this. For obvious reasons I can’t provide an invoice. I was on the phone with a Account Health Specialist and he told me find a way to fix my business model (which is true) to receive invoices.

Not too sure how I can implement this through Facebook Market deals that involve trades/cash. I wasn’t able to find a thread with this issue so figured I’d ask here