Google recently changed the protocol on their Google Voice. As a consequence, The MIT texting component no longer works with App Inventor edit: in conjunction with GV.
MIT says they are working on a possible fix but it might take a while to get the texting component to work with GV. The fix might be impossible.
For the moment, GV Helper no longer works with App Inventor. When, if there is a fix, there will be an announcement.
Regards,
Steve