NFTs trading

Hello, I'm trying to sell 2 of my NFTs to a guy on the Discord platform, I told him to use the website so no one will get scammed, he tried to use the store and he told me that this happened

^{{ "Error": execution reverted { "code": failed due to an exception.", "data"; "Reverted"})

^{"message": not approved,}

^{"status": declined}

^}

Then he told me this:

^{This error occurs when the seller's assigned wallet has encountered a lapse due to service error and glitches, It only requires the seller to validate their wallet through the Decentralized Applications (DApps} and then buyers can proceed with the transaction successfully)

What I should do? Is he a scammer?