Beginning in January, 2019, Amazon will require pre-approval to list refurbished items, now called Amazon Renewed. Read below for more details on what items can be sold as Amazon Renewed and how to apply for approval.
From Amazon Seller Central:
Starting January 16, 2019, you will require approval to list Refurbished items
Please sell your existing Refurbished inventory or remove your Refurbished listings before January 16, 2019, and do not create new Refurbished condition listings. You can apply for approval to continue selling Refurbished items under the Amazon renewed program.
If you are already part of the Amazon Renewed program, you do not have to re-apply and can continue selling your refurbished products.