Integrating with AWS Textract

I am trying to integrate with AWS Textract (documentation found here: https://docs.aws.amazon.com/textract/latest/dg/textract-dg.pdf). Particularly I am trying to use the AnalyzeDocument operation first. I am getting the error highlighted below. Has anyone been able to integrate Appian with AWS?

I am using Appian 194 which already has the AWS Signature Version 4.

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