I have a Kindle Fire 2nd generation which is an older model. I noticed over the weekend this app quit working. When I clicked on ot it said something about this app is not supported by this version of andriod or something like that. I am assuming this older model of Fire is not supporting many of these apps now. I have had a couple of others to quit working too. One of them was the NCAA March Madness app.
My wife has a Kindle HD. The Fios app is working on that . I checked it last night. I just had to download the newest version and it seemed to work just fine. The March Madness app works also on this Fire HD. My guess is that Amazon is trying to phase out these older models by not updating these apps to keep working on these older versions of a Kindle Fire.