Help & troubleshooting for channels on your Roku device, including adding/removing channels, logging in to, authenticating, or activating a channel, channel-specific playback issues, assistance contacting channel publishers to report issues, and adjusting channel-specific settings.
They can't support the app, it isn't theirs to set up. I don't understand how you don't understand that. Would it be nice? Sure, but I can name a million other things that would be nicer of them to do.
Have you contacted Amazon yet to ask why they haven't enabled the Amazon Prime Roku app for your location?
Try removing the channel from the Roku home screen by navigating to the channel tile, pressing the * key on your remote and choosing 'Remove channel'. Then restart your device from Settings>System>System restart. Once your player starts up again, add the channel back once more.