

While iTunes Connect is unavailable, Apple will not accept new apps or app updates, which means all pricing changes and new app submissions will need to be locked in before that date for developers who wish to offer discounts or new content over the holidays.
Developers tend to offer sales and promotions ahead of when the App Store closes for the holidays, and those sales remain available until the App Store re-opens in late December.
While App Store submissions will be unavailable, other iTunes Connect tools will remain accessible to developers throughout the holiday period.
Article Link: Apple to Shut Down iTunes Connect From December 23 to December 27