This Roku 2 was working flawlessly with Prime under a different account for years until this sudden problem.
I am having this same problem. I click on Amazon Prime it goes to load it then bounces back to the main menu. I know that amazon prime video works, because it works on my other tv. I have the Roku ultra and it is less then 6 months old. I tried the disconnect reconnect and that did not work. I tried system restart, I have checked and it does not need an update. I see where Others say to delete the program and restart. I can’t figure out how to delete a program. It was preloaded on the main menu. I have not had to add any programs.
It works until it happens again. I've had to go through this process several times since buying my Roku tv. It doesn't happen on my other tv that has the simple Roku stick. Roku should fix this issue as it is a huge inconvenience to go through this process when you have friends over to watch a movie.