Hi supermorgen,
Firstly please try steps below to solve the problem:
- Run your Outlook client in safe mode to check if the issue is due to add-ins.
- Try to reset the navpane of Outlook client by typing Outlook.exe /resetnavpane and click
OK.
- Try to troubleshoot the issue with Support and Recovery Assistane for Office 365 (SaRA), you may find instruction about it
Here.
If methods above couldn’t address the issue, please confirm following information:
- Was the “normal” option accessable before?
- Did you make any modification before this issue occurred?
- Do you encounter the similar issue in other computers?
To make sure, please provide the screenshots regarding the issue and your Outlook client version as below.

Your time is much appreciated.
Regards,
Kevin