Thanks for the posts.
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.
If you are still unable to resolve the issue, you'll want to contact Amazon Prime support directly to inquire further. Many channels on Roku are developed and maintained by the channel provider themselves.
Roku Community Moderator