Over the past few days, a security issue came to light regarding an authentication service used by another tool, acd_cli. acd_cli had its authentication keys for Amazon Cloud Drive blocked after Amazon engineers reviewed their source code for their authentication service and found a security issue.
This morning, rclone's authentication keys were apparently blocked by Amazon. No reason has been brought forth at this time, and rclone does not use a cloud service to authenticate users - it uses a local web server. Theories include an influx of rclone users after acd_cli was blocked, people extracting the API authentication keys from rclone and using them with acd_cli, a combination of both, or Amazon wanting to clamp down on heavy users with several terabytes of data, and blocking the tools they use to do so.
The Amazon rep that I spoke with over the phone speculated that it "may be because of a recent event," but offered nothing more. I was offered a full refund, four month