sakdc,
I'm really bummed it didn't work for you. I didn't realize the old FIOS Mobile app had been removed from the Apple app store. It's still available for Android. I encourage you to try a combination of uninstalling and reinstalling the FIOS TV app and auto-correcting your STB. There must be some combination that will work. I'd do it myself but I am not going to mess with it now that I have something that works. It seems to be a fragile system. I wish FIOS cared enough to prioritize this problem.
(You could always buy a cheap android phone to use the old app, and just keep it at home connected to your wifi, without attaching a calling plan to it.)