1. Open the outlook desktop application
2. In the upper left, click on file.
3. click Info > account settings > account settings
4. Select the email tab > double-click on your email name, > then in the next window, click More Settings.
5. click on the advanced tab> uncheck the box that says "turn on shared calendar improvements."
close out of Outlook and re-open it. It may take a few minutes to load after this. If you run into any errors after this, you may need to reboot your computer for the changes to take affect.