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 making use of shared calendars in Outlook 2016 you may find that not all appointments are showing in the calendar or are disappearing.
Typically this happens when running Outlook 2016 in cached mode with exchange or Office 365.
This also made large public folders slow to use as the contents needs to sync down every time you switched to the folder.
This issue was fixed in the in the January 3, 2017, update for Outlook 2016 (KB3141453) for MSI installations.
To edit a shared calendar, go online to your own calendar, open Calendar for Windows 10, or use a mobile device. Last updated: May 2, 2017 ISSUE When you try to accept a shared calendar using your Office 365 for business account in Outlook 2016, you might receive the "Something went wrong" error or your sign-in might fail.
STATUS: WORKAROUND To access the calendar shared with your Office 365 for business account, you’ll need to accept the invitation from Outlook on the web .
Users with the Click to Run installations (most people) will see the fix soon, if not already.
A Microsoft Outlook Most Valuable Professional (MVP) since 1999, Diane is the author of several books, including Outlook 2013 Absolute Beginners Book.
What if the Outlook (2010, 2013) user has checked the “download Shared folders” to cache all Shared folders locally ?