This seems to be the most pertinent thread for my question, even if the last post is a year old. I voluntarily chose to use PlatePass and fully opened the transponder on my Hertz rental out of BOS a few days ago, but every time I went through a toll gate I would either not get a green light, get a "Call Service Center" message or, at the Baltimore Harbor Tunnel, got a red light with the "Invalid Tag" message. I understand from the official EZ-Pass FAQs that this usually means that the transponder account balance is below zero.

Do I need to take any action in this situation, or will they take care of any fines or violations incurred automatically? In any case, in the context of the rather high service fees I accepted just for using the tag I would really expect them to keep their account funded properly...