Updating the offline address book
When it didn’t or when you want to make sure you do have the latest OAB available, you could manually trigger an update from within Outlook as well.
By default in Exchange Online, the Address List role isn’t assigned to any role groups.
You need to be assigned permissions before you can run this cmdlet.
Although all parameters for this cmdlet are listed in this topic, you may not have access to some parameters if they're not included in the permissions assigned to you.
Is there any way I can force a manual update of the Offline Address Book (OAB) in Outlook or reset it completely otherwise?
In general, Outlook will automatically update the Offline Address Book (OAB) for Exchange accounts once every 24 hours.