There is a bug in the Calendar's Day and Week view that causes all day events to disappear when the window size changes. Adjusting either Outlook's window size (either the height or width) or the calendar size (by adjusting the width of the navigation pane or to-do bar) will show or hide the all day events.
Additionally, the "show more" arrow will not work and the scroll bar on the all day event section is disabled. Rather than expanding the all day event section so more events are visible, clicking on the arrow icon opens a new appointment form or returns an error.
Now you see the event:
Now you don't. Make the window just a little wider and the event disappears:
The fix? Reset the view. To do this, you can either open Outlook using the /cleanviews switch or just reset the Day/Week/Month view. Note that resetting the view is a temporary fix wile using /cleanviews has a more lasting effect but wipes out all custom views.
To reset the view on the folder, go to View, Current view, Customize Current view. Click Reset on the Current view dialog.
Hi do you know if this affects any particular version of Outlook?
It originally showed up in 2007 I believe. AFAIK, It should not be a problem in 2016/2019/365. If you see it in current versions, reset the view.
It seems to be back today in Outlook 365.
Getting very frustrated with a long-time app that just doesn't work well. Had worked with support for more than 3 months regarding a problem in Outlook for Android, and I'm still waiting for it to be fixed!
I will Google this question, but an answer here would be helpful: how does one "open Outlook using the /Cleanviews switch?"
Right click on the Start button and choose Run or press Windows key + R to open the Run command, type or paste the following into the Open field then press Enter or click Ok. (there is a space before the /)
outlook.exe /cleanviews
Thank YOU! This worked for Me!