Cannot save Amazon SP API Settings

I receive this message when I save Amazon SP API Settings.

Error: invalid_aws_credentials
Error Description: An error occurred (InvalidClientTokenId) when calling the AssumeRole operation: The security token included in the request is invalid.

Amazon no longer provides AWS credentials or AWS IAM for Private Developer because they are not needed. See Amazon announcement:

https://developer-docs.amazon.com/sp-api/changelog/sp-api-will-no-longer-require-aws-iam-or-aws-signature-version-4

Refresh Token, Client ID and Client Secret were assigned by Amazon through Amazon Seller Central->Developer Central.
I filled AWS IAM, AWS Access Key and AWS Secret Key with random values because they are required fields for the form.

Ecommerce Integrations: v1.19.6 (main)

ERPNext: v14.65.3 (version-14)

Frappe Framework: v14.67.1 (version-14)

Start by tracing the Amazon SP API settings save flow described in the report, focusing on the required AWS IAM, access key, and secret key fields and the invalid_aws_credentials error. Compare the current form requirements with Amazon's linked announcement; done means Private Developer settings can be saved using the refresh token, client ID, and client secret without obsolete AWS credentials.

Written by the indexing model from the issue text.