Much of my work the past few years has been working with Amazon's seller-side e-commerce APIs, and it's truly infuriating how impenetrable their "support" systems are. It's ridiculously hard to get even basic problems solved, and for some reason they make it near-impossible to get access to shipping and tax addresses via their APIs [0], which makes developing pretty basic functionality really difficult.
[0]: https://github.com/amzn/selling-partner-api-docs/discussions...