Using Classic Outlook on Windows for personal email, calendar, and contact management
Hi Casey,
May I know which Office 365 version are you using? Please provide us with the detailed information screenshot about this, see What version of Outlook do I have?
Please try using Outlook in safe mode and disable all add-ins to check this issue.
To start Outlook in safe mode.
Choose Start > Run.
Type Outlook /safe, and choose OK.
You may refer to the article to Repair an Office application to check this issue.
If you are Office 365 for business subscribers you can use the Office 365 Support and Recovery Assistant (SaRA) tool that can diagnose and fix the Outlook problems.
Please download the tool and run the Support and Recovery Assistant on the affected computer troubleshoot the issue. See: Fix Outlook and Office 365 issues with the Support and Recovery Assistant
Best regards,
Shyamal