I had been trying for 3 days for the same problem. I even ended up trying and being able to install
the Roku app on my Chromebook and my android phone, so I was figuring there has to be an
answer to watch on tv. In my own case, not that this would work for anyone else, I had to let the
entire movie play to the end on my Chromebook, and had the sound turned down and didn't watch
it, just let it play to the end. I had noticed that if I held the home button down while trying to watch
on my tv that some of the scenes looked like they were downloading as they were being played
on my Chromebook. So the whole movie played to it's ending, I then went back after unplugging
and reattaching the firestick and plugging in the tv (I just unplugged all the equipment while
I was "downloading" the movie onto the Chromebook), I then could view the movie on my tv.
Hope this helps. It is pretty annoying to know that the channel is free and you can't watch it!