Hi @JustinMicheal-7973,
I have removed and re added the permissions more than once but still no joy.
What permissions does the user have? Assuming you are running Exchange Online, you can connect to Exchange Online powershell and run the following command to check the permissions:
Get-MailboxFolderPermission -Identity sharedmailbox@contoso.com:\Calendar -User user1@contoso.com
Based on my research and test, we can add the user as a delegate with access to private items in order for the user to see private items in Outlook client:
If this is not the current settings in your scenario, please run the command below to adjust the permissions and see if it works:
Remove-MailboxFolderPermission -Identity sharedmailbox@contoso.com:\Calendar -User user1@contoso.com
Add-MailboxFolderPermission -Identity sharedmailbox@contoso.com:\Calendar -User user1@contoso.com -AccessRights Editor -SharingPermissionFlags Delegate,CanViewPrivateItems
If an Answer is helpful, please click "Accept Answer" and upvote it.
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.