Unable to reset administrator@vsphere.local with vdcadmintool (failed 9100)

I'm trying to reset the administrator@vsphere.local password but it fails every time...

I'm using this document : VMware KB: Cannot change the administrator@vsphere.local password after upgrading from vCenter Server 5.1 to 5.5

But everytime I try it fails with code 9100:

Here is my log:

==================

Please select:

0. exit

1. Test LDAP connectivity

2. Force start replication cycle

3. Reset account password

4. Set log level and mask

5. Set vmdir state

==================

3

  Account DN: cd=administrator,cn=users,dc=vsphere,dc=local

VmDirForceResetPassword failed (9100)

Anyone know how to fix this ??