Using Outlook for Android for personal email and calendar management
It seems that I had the same issue since las week !
First, I cleared cache, uninstall and install back --> It works during 1 week until this evening !
But today I fixed by removing calendar widget on my home !
It looks like than the problem (in my case) come more from widget than outlook !
If you have the same issue and the widget try to remove it and reopen outlook and tell us if it works !
Good night and sorry for my english !