Using Classic Outlook on Windows for personal email, calendar, and contact management
Hi Holly_980,
Thank you for providing detailed screenshot. May I know which Outlook 365 version are you using, please refer to the article and provide us with the detailed information, see What version of Outlook do I have?
You may try temporally Set Proofing Language to another language and restart Outlook then change back to the English (United States) also select the Detect language automatically check box to see if there any improvement.
Does this issue happen to any other users in your organization?
Moreover, if you are Office 365 Business subscriber can use the Office 365 Support and Recovery Assistant (SaRA) tool that can diagnose the Outlook problems and create another profile to check this issue. See: Fix OutloFix Outlook and Office 365 issues with the Support and Recovery Assistantok and Office 365 issues with the Support and Recovery Assistant
Your patience and cooperation will be highly appreciated.
Best regards,
Shyamal