Issue: I'm unable to open a group of calendars in Outlook. I get the error message "We can't add the calendars of everyone in this distribution list <distribution list name>. Please add each calendar individually."
Environment: Outlook, Windows, Office 365, Calendar
Resolution: Turn off "Shared Calendar Improvements" in Outlook:
1. Open the Account Settings dialog in Outlook by navigating to File > Account Settings > Account Settings
2. Select the Change button in the ribbon
3. Select the More Settings button in the Exchange Account Settings dialog
4. Navigate to the Advanced tab and uncheck the box for Turn on shared calendar improvements
5. Select Apply, then OK, then close out of the Exchange Account Settings and Account Settings dialog boxes. Close and restart Outlook. Then you may open calendar groups from the address book.