Apple today announced its traditional recession period. App Store Connect, that this year will happen from 23 to 27 December.
During this time, the platform through which developers can submit new apps or updates for the approval of the Apple team will be unavailable.
The only way for an app to be launched / updated during this period is through scheduling, obviously with preliminary approval from Apple.
Apart from releases and updates, the rest of the App Store Connect features (such as accessing app statistics, for example) will remain available.