Thanks for the efforts, SusanMaryland. I had high hopes. Your fix sounded like a very plausible solution. (I'm in DC, btw. Sounds like your Fios TV app was "borked" at the same time as mine. Wonder if it is a regional issue?)
But then I tried this fix. It didn't work for me on the new app and, unfortunately, I had already deleted the old TV app on both of my ios devices. The new app had been streaming well for me before this week (even if the UI was terrible).
For those who want to try this fix, there is one extra step to Susan's instructions: After "main menu" you must click on CUSTOMER SUPPORT menu to find "top support tools" etc.
In any case, it was good to discover these tools, which I hadn't noticed before. Thanks, again!