Hi,
Is this a problem that has only recently occurred? If so, what specific operations did you do before this problem occurred?
What's the version of your Outlook client? (File > Office Account > About Outlook). Please make sure you have upgraded your Outlook to the latest version.
In this situation, please try exiting Outlook desktop client and see if the issue can be reproduced on your web mail.
It is also suggested to use Outlook Search Repair tool to repair your Outlook for Mac.
Any update, please feel free to post back.
Regards,
Aidan Wang
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