Do your users have Administrator rights for the Server?
This issue might be due to an underlying windows function NetUserChangePassword()" that cannot be used for Non-Admin users.
The Windows Password can only be changed when the user is an Administrator using the specific windows API.
The only way a non-Admin user can change his password is using the standard Windows method by pressing Ctrl-Alt-Delete and go to the Change Password option presented using the normal windows dialogue.
Note - I am assuming you have Windows OS at Server.
Other way what you can try is -
Go to command prompt on your server - > Go to the path for $BSE\bin - > And try following commands
2) badmin -p -chkpwd username
Check what it returns. If it says, "Aging is turned off". you need to turn on the Aging mask form LN.
Unless you try to do something beyond what you have already mastered, you will never grow!