Reset password on Subaccount Yahoo mail

I have been trying to reset a password on one of my sub account emails addresess @sbcglobal.net.  I go into manage sub accounts and put in the email address i need to reset.  I then input the Last Name.  I get an error saying hmmm.....we can't reset your password.  We don't have the account details needed to complete your request.  

I then log into the main account and go to Manage Sub Accounts, but there is not an option to reset a sub account password on this page.

How can i reset a Yahoo subaccount email password?