In some cases it might happen that Exchange Offline Address Books do not get synchronized, even after days of waiting, workstation and server reboots.
Maybe it does not detect the change itself, e.g. if a dynamic distribution group is deleted and another group is created with the same name.
For the workstations, delete the cache files under AppData\Local.
Batch script example (run it e.g. via GPO at user login):
del /f /s /q "%LOCALAPPDATA%\Microsoft\Outlook\Offline Address Books\*.*"