This error occurs when a seller is only authorized to sell products using the Amazon Fulfillment Network (AFN) due to policy violations, seasonal restrictions, or customer complaints. If you are trying to sell using Merchant Fulfillment Network (MFN), the offer will be un-buyable. If you have already chosen AFN as your fulfillment channel and your offer is live for sale, you can ignore this error. However, if you have confirmed that the SKU is listed as AFN and find that the offer is not live, contact Selling Partner Support.
If you would like to list through MFN, verify as mentioned below: