The default refresh interval for the sync of contacts between the LDAP server and the ICON is 12 hours. This can be made immediate update by moving to directory icon from the remote.
If the refresh does not work until a Reboot is required for the ICON.
1. Check the port configurations, host name/password and port number should be correctly configured. The port is 389.
2. If a Unregister button is clicked ever then the auto sync of update would fail even though the status shows as "Registered".
3. A Reset will help in such cases and re-configuring the LDAP settings.