We can't add the calendar for.... right now. Please try again later

Problem

When using Microsoft Outlook and attempting to access someone else's calendar, you receive an error message like, "We can't add the calendar for.... right now. Please try again later." 

Solution

Disabling Microsoft 365's shared calendar improvements may resolve the issue. The following steps have fixed this problem for other people.

1. Open the Outlook app.
2. Click File.
3. Click Account Settings.
4. Click Account Settings (again).
5. In the Email tab, click your email address to select your account.
6. Click Change.
7. Click the More Settings button.
8. Click Advanced.
9. Clear the "Turn on shared calendar improvements" checkbox and click the Ok button. 

10. Click Ok on the, "You must restart Outlook for these changes to take effect" model dialog box"
11. Click Ok.
12. Click the X in the upper right hand corner. You do NOT need to click Next.
13. Click Close.
14. Close and reopen Outlook.

Additional Resources

For additional information, view Known issues with shared calendars in Outlook.