Hi! I have the same annoying issue signing in with my Amazon Fire Tablet. I just chatted extensively with a Roku agent for them to tell me it must be an Amazon issue. Like I disagree if I couldn't access the Roku app completely on my tablet then maybe I would agree but since it says my login information doesn't match their records or something to that effect when like you said I know for a fact it's the right email and password information cause works on my other devices. Have you had any resolution to this problem? Did you find a way to login via your Amazon tablet? If so please let me know in a reply. Thank you. And if anyone else has a solution to this problem please reply. Have a great day!
I see Roku has not addressed this issue for many months beyond asking the same troubleshooting questions.
I have the same issue and it's driving me nuts because there's content I can't access any other way.
Why disable it on a fire tablet when it works perfectly on a fire stick??
I can't access the app on my Kindle, but I can log in via the web browser and watch content. You may want to try it that way...