Apple will celebrate the Christmas holidays by closing its main services for a week, from December 22 to December 29 inclusive. This became known from a blog post for developers.
The company will disable iTunes Connect, iTunes Producer and iTunes Connect for iOS. During this period, developers will not be able to upload new apps to the App Store or update already downloaded ones. It will also not be possible to change the cost of IAP and applications.
All changes that developers are planning for the holidays and dates close to them should be reported to Apple no later than December 18.
The services will start working in full on December 30.
Note that Apple holidays are an annual event, so they will not come as a surprise to developers.
A source: https://developer.apple.com