Hi,
Only one user have this issue or all users have?
Please check the related settings of OAB according to the following settings:
1.Please run the following command to update the offline address book and try to download again.
Get-OfflineAddressBook | Update-OfflineAddressBook
2.Please hold down the ctrl key and right-click the small Outlook icon, click "Test email auto configuration" to check whether the Autodiscover service is running normally.
3.Please run the following command to check the settings of OAB virtual directory:
Get-OabVirtualDirectory | fl name, *URL*
4.Please run the following command to check the setting of OAB:
Get-OfflineAddressBook | fl
5.Please run the following command to make sure the organization mailbox is exist:
Get-Mailbox -Arbitration | where {$_.PersistedCapabilities -like “*OAB*”} | ft Name, Servername, Database
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