Fake Airpods

Hello,

I believed I received fake airpods from a 3rd party app (Mercari). I put the serial number to verify through Apple and the site says it's valid however I am receiving an error on my iphone while trying to connect stating "Cannot verify airpods, These headphones could not be verified as genuine Airpods and may not behave as expected".

I need a formal document from the manufacturer stating these are not authentic but I am unsure on how to get this. Any help is much appreciated.

Thank you.