Unable to set "User can not change password" account attri..

Hello,
I have an application to manage AD account. This application uses ADSI.

On my test setup I am able to set the "User can not change password"
for user account.
But the application fails to set the same on production environment.
Moreover I can set this flag manually by logging into the production
domain.

The application has domain admin rights.

I am not able to figure out what is preventing from setting this flag
on production AD?

Any help will be great.

Thanks & regards,
Hemant