Every year for the holidays Apple shuts down its App Store Connect tool in December. The company issued a notice today reminding developers of the schedule.
App Store Connect Holiday Schedule
The busiest season on the App Store is almost here. Make sure your apps are up to date and ready for the holidays, as new apps and app updates will not be accepted December 23 through 27 (Pacific Time). Please ensure time for your releases to be scheduled, submitted, and approved in advance. Other App Store Connect and developer account features will remain available.