To ensure a smooth holiday selling season, your ability to migrate your Seller Central account to the new Shipping Settings will be disabled on December 12, 2015, and re-enabled in early 2016. During this time, you won't see the option to migrate on the Shipping Settings page in Seller Central.
You can choose to remain on the current Shipping Settings platform or choose to migrate to the new Shipping Settings before December 12.
To migrate to the new Shipping Settings, open "Shipping Settings" (https://sellercentral.amazon.com/gp/shipping/dispatch.html) and click the "Migrate Now" button.
If you have already migrated to the new Shipping Settings, then you can disregard this notice.
Regards,