Hi,
Is this issue only affecting one particular user, while the others who have access to the shared calendar can see the up-to-date calendar?
If this describes the situation, I'd like to suggest trying to clear the checkbox of "Download shared folders" via File > Account Settings > Account settings > double click the account > More Settings > Advanced , then restart Outlook and check the result:
If the issue persists, you may consider recreating a new Outlook profile for the problematic user and see if there would be any improvement.
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