They have done away with the ability to reset the subaccount passwords. In addition, if you have a very old set of subaccounts, you have a problem where you have probably not set a security question for them.
What happens when you try to reset is you actually end up getting a PIN for the primary account, which i am sure is not what you were trying to reset.
The only way i have found to fix this is to call VERIZON support, get them to change the password, and once you can get in, set a security question. Write the info down somewhere or you'll have to do it all again later.
Very fustrating that they can't do this right, it should be simple for them to just allow the individual to fix thier own email.