Symptoms
When you try to delete the free/busy configuration on a mailbox, you can't add or re-create any necessary delegate permissions.
Causes
The ResetDelegateUserCollection parameter of the Remove-MailboxFolderPermission cmdlet doesn't exist in Microsoft Exchange Server 2019.
Resolution
To fix this issue, install the following cumulative update:
Cumulative Update 14 for Exchange Server 2019 or a later cumulative update for Exchange Server 2019