Cross Exchange Org migration - missing Self permissions

Some users are getting the following errors when trying to share calendars:
This was a cross forest intra-org migration.
I use the prepare script
I had used the Exchange 2010

From calendar view clicking on share calendar:
outlook share permissions could not be displayed. permission information for this folder could not be accessed.

delegates
the delegates is not available unable to access outlook folder



answer is to use
Add-MailboxPermission -Identity 'username' -User 'NT AUTHORITY\SELF' -AccessRights 'FullAccess' -InheritanceType all
or
to run it for all mailboxes:
Get-Mailbox | Add-MailboxPermission -Identity 'username' -User 'NT AUTHORITY\SELF' -AccessRights 'FullAccess' -InheritanceType all