I downloaded the Roku TV app to my Amazon Fire Tablet 10 (running Fire OS 7.3.3.0 - Fire HD10, 11th Gen).
The app will open, but if I want to sign in (which I do), it won't accept my login ID/password combo. I know I have the right ID/password combo as I then used them to log in to the Roku site and make this post.
So, what about the Fire Tablet 10 and the Roku TV app is leading to this incompatibility? I care as I want it to keep track of what I've watched, what I have left to watch, and my list of things I'm planning to watch later.