Hi @Becky Taillon ,
According to my research and test, the issue appears to be caused by enabling shared calendar improvements. You can turn off it follow the below steps:
In Outlook, select File >Account Settings >Account Settings.
Select the Microsoft Exchange account and choose Change....
Choose More Settings, followed by the Advanced tab.
Unselect the checkbox next to: Turn on shared calendar improvements.
Restart Outlook and check.
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