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.
I'm not certain that Amazon has authorized their Roku channel for that country. It is up to Amazon to configure their channel for the countries allowed. Unfortunately, there's no way around that restriction. Roku has no control over that.
Be aware that you might be able to use Amazon Prime with a computer browser in India, but they might not authorize streaming devices to use it. So it's not just an issue of Prime being available in India. They have to permit the various devices to access it as well.
Dan Nvidia Shield, Roku Stick (3600), Ultra (4640), Premiere (3920), Insignia 720p Roku TV, Sharp 4K Roku TV, Windows 10 Pro x64 running Serviio and Plex on a wired Gigabit network.