We’ve just got this.  The team is working through it, and having made a YF-3 model, is pretty cool seeing the background story to the decision.

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AccessDeniedAwsUsers|The Access Key Id AKIAIEKYLVAQVWSCL4RQ is not enabled for accessing this version of Product Advertising API. Please migrate your credentials as referred here https://webservices.amazon.com/paapi5/documentation/migrating-your-product-advertising-api-account-from-your-aws-account.html.
]