Recently we found out that we had to reset the admin password due to it being locked and, I think, expired. VMware does have a KB on how to this can be done:
However, what it fails to mention is that an additional step may be necessary
Now, if you just reset the admin password, it will allow you to logon via SSH as admin to the appliance. However, if you try to logon as admin to the admin GUI interface, you may encounter incorrect user name/password error. This is corrected by performing the stops in the 2nd KB article.