Fail to register system to RHN

Issue

When use rhn-channel to list available channels:

[root@server4 ~]# rhn-channel -L
Username: <username>
Password: 

Traceback (most recent call last):
  File "/usr/sbin/rhn-channel", line 145, in <module>
    main()
  File "/usr/sbin/rhn-channel", line 137, in main
    channels = get_available_channels(OPTIONS.user, OPTIONS.password)
  File "/usr/sbin/rhn-channel", line 97, in get_available_channels
    for channel in client.system.listChildChannels(key, int(system_id)):
  File "/usr/lib64/python2.6/xmlrpclib.py", line 1199, in __call__
    return self.__send(self.__name, args)
  File "/usr/lib64/python2.6/xmlrpclib.py", line 1489, in __request
    verbose=self.__verbose
  File "/usr/lib64/python2.6/xmlrpclib.py", line 1253, in request
    return self._parse_response(h.getfile(), sock)
  File "/usr/lib64/python2.6/xmlrpclib.py", line 1392, in _parse_response
    return u.close()
  File "/usr/lib64/python2.6/xmlrpclib.py", line 838, in close
    raise Fault(**self._stack[0])
xmlrpclib.Fault: <Fault -208: 'No such system'>