Using older versions of Outlook for Mac for personal email and calendar
I tried all of the steps mentioned here, and also some steps on other sites. Nothing worked.
So, as a last ditch effort, I dragged the "MainProfile" folder out of the "Outlook 15 Profiles" and put it on the desktop.
Then waited about 2 seconds, then dragged it back into the "Outlook 15 Profiles" folder.
Immediately fixed the problem.
Hope this helps.
I hoped your solution was helping me, but I didn't.
I have also the problem after using time machine.
I have move the MainProfile folder and put it back.
Went back to outlook and .... nothing happend.
It is really customer unfriendly from Microsoft to not help paying customers.
Especially the fact that they know about the problem from nov 2018.
Really unacceptable.