NFTs minted through the Verisart Shopify App are automatically issued a Certificate of Authenticity once the NFT is claimed by the customer. You do not need to configure this manually. The certificate will include the on-chain information and will automatically get transferred to future new owners when the NFT is traded.
If you have encountered an error message like the above when adding an item in the Certificates tab, please ensure that the item is not an NFT prior to proceeding. You will be able to see this in the Shopify Products tab.