As noted by MacStories, Apple has sent out an email informing developers that it will be shutting down the iTunes Connect portal for the App Store over the Christmas holiday as it has the past several years. This year's shutdown will extend from December 22nd through 29th, two days longer than in past years.
We strongly recommend that you do not schedule pricing changes through the interval pricing system in iTunes Connect that would take effect from December 22 through December 29. Pricing changes scheduled to take effect during this date range will not be reflected in the App Store and the app will become unavailable for purchase.
We also recommend that you do not schedule any apps to go live during the shutdown. Releases scheduled with a sales start date between these dates will not go live until after the shutdown.
Most of Apple's corporate employees in the United States will also be taking all of next week off in recognition of the company's success this year, but the company has made no announcement about whether this will include employees responsible for app reviews and other App Store functions.