AirPods warranty coverage/authenticity issue

I bought a pair of AirPods gen 2 off of Kijiji and they were brand new, had never been used and the plastic was still on it. They are authentic Apple AirPods, but I had troubles accessing the Bluetooth menu for them. I checked to make sure that they were real AirPods, and the website gave me this message, “

We’re sorry, but this is a serial number for a product that has been replaced.” etc. What does this mean?