The update is blocked, because cool-solutions are installed.
Component 'cool-solutions' is not yet available
The Cool Solution Repository for UCS 4.4 is now available. You can now update by setting the UCR variable, shown in the message block.
However, most Cool-Solutions are not yet adapted and tested. So it may happen that they don’t work.
In the linked Wiki https://wiki.univention.de/index.php?title=Category:Cool_Solutions you can see if the Cool-Solution is already released.