Samba/Winbind issue - Can't get user and group info from sub domains

Hi,
We now have a Samba or Winbind issue. The Linux client under RHEL6 can not get Windows' AD sub-domain info. See the following output please. The main domain 'Global' is shown online, but the sub-domain 'Europe' and 'Asia' are shown offline although they are online.

Commands 'wbinfo -u' and 'wbinfo -g' only show users and groups under the Global domain, but not the sub-domain Europe and Asia.

How could this happen? Do we need to join this Samba client to the sub domains separated?

Please help. Thank you much in advance!