Make sure that for your authentication on your sub accounts you are using the sub account's username and password, not the primary account's info. Also make sure that they are properly formatted. Without looking at your settings there's not much else I can tell you, but there are online repair tools available from Verizon if that would help.
You can also contact tech support and have them review your settings. I would suggest via chat, since there seems to be a higher competence level for the chat reps (in my experience).
You can look on their Contact Us page for options.