Hi @Jim Sizer
Welcome to our forum!
What is your account? Microsoft 365 or something else?
And whether the error occurred on your personal calendar or a shared calendar?
Does the error occur on the Outlook desktop client? To further confirm if the issue is more related to Outlook desktop client, if possible, please log in to your web mail and do the same test to check if the issue persists.
Meanwhile, here are some steps you can try to resolve it:
- Update Outlook:
- Ensure your Outlook is up to date. Go to File > Office Account > Update Options > Update Now
- Clear Offline Items:
- Ensure your Outlook has enough space. Go to Right-click your calendar, select Properties>Under General, check Folder Size and clear Offline Items.
- Use Microsoft Support and Recovery Assistant:
- Refer to the link and create a detailed scan of your Outlook Calendar to identify and resolve issues.
- Review Calendar Permissions:
- If the error occurred on a shared calendar, ensure you have the necessary permissions to edit events in the shared calendar. Sometimes permissions can change or get updated incorrectly.
Hope it helps!
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