Next time you have connection to your server, Outlook will sync every change you made when you were offline.
The easiest way to verify this is the problem is to log in to your Outlook Web Mail, if you are using Office 365 you can log in at https://portal.using your username and password.
If you can see the appointments in your shared calendars online then the issue is more than likely due to the cache on your Outlook needing refreshing, here are the steps to fix the problem: Please note.
If you are not sure that you are using hosted exchange please do not follow these steps as incorrectly deleting the Outlook data file may delete your Outlook email permanently.
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