Hi
I just received the following answer from Microsoft. Seems like the closed upgrade windows until 11/30 and the they will reopen it again. I wish they post such information somewhere that we know in advance.
From Microsoft:
"Well, based the screenshot you shared me, the situation is that your client had scheduled an upgrade of the environment, which should have been for yesterday or today, the issue is that the upgrade window is currently under maintenance, which caused that the update will not be performed. As I mentioned in my last email, until Tuesday 30th the upgrade window will be available again, then until that date you can schedule the upgrade. So, answering your question, Yes it will fix the issue."