Offline Address Book: Only downloads every 24 hours. If you alter an address or add a user, you will not see them until the 24 hour update period or if you force an offline address book update.
Manually update OAB:
Open Outlook
Click on Send/Receive tap
Choose ‘Send/Receive Group’
Click ‘Download Address Book’
Select ‘Download changes since last Send/Receive Address Book’
This will force an address book update