Ah, gotcha, I missed the conundrum before… sorry for the slowness 
Interesting some are not showing as not supported. Still leaning on Amazon’s side for this one, but just a guess, and my inference is that this capability came from the new Dashboard Amazon deployed for some of their hardware
Only thing I can think of is, latest alexa app? Maybe a log out and log in to “goose” the app? Or a cache flush?
I just looked on my FireHD 8 and “live view” option isn’t even available on that device… looking to see if there is an update.