Apple today reminded developers that new apps and app updates will not be accepted through App Store Connect from Monday, December 23 through Friday, December 27.
Any app releases should be scheduled, submitted, and approved in advance.
This brief closure of App Store Connect occurs every holiday season. Other features of App Store Connect will remain available.
https://www.macrumors.com/2019/11/29/app-store-connect-holiday-schedule-2019/