We have a hybrid config., with some mailboxes in Office 365, and some mailboxes on-premise.
An Office 365 mailbox cannot view the calendar of an on-premise mailbox, and vice verse.
Error in Outlook trying to open a shared calendar ‘could not be updated’
Error in Outlook trying to view calendar of another mailbox using Scheduling assistant ‘could not be updated’ as below screen
Error in OWA opening a shared calendar ‘This folder couldn’t be opened. You might not have permission to open it, or it might not exist anymore’
Now the solution will be to run the both command on the exchange server:
Set-AutodiscoverVirtualDirectory “SERVER\Autodiscover (Default Web Site)” -WSSecurityAuthentication $True
Set-WebServicesVirtualDirectory -identity “EWS (default web site)” -WSSecurityAuthentication $true
This two command solved my problem