Announcement reposted from Amazon:
On August 15, 2023, all domestic and out of country MFN sellers will have the 2-day Default Handling Time option removed from Shipping Settings in Seller Central and have their accounts automatically update to 1 day as the default handling time. This change will only affect default handling time for Merchant-Fulfilled-Network SPs and current SKU level handling time configurations will not be affected as a result of this change. In other words, only SKUs that have no specific handling time set will be affected by this change, and will follow the new default handling time of 1-day.
In case you have specific products that may take longer to be shipped, you can set a longer handling time at SKU level that will override your default handling time for orders of these products. For more information, including how to modify handling time for specific products, see Change handling time Help Page