Architect Data Action 403 on Lambda Invoke

Hitting a wall calling an AWS Lambda from Architect. The Data Action hits POST /2015-03-31/functions/{fn}/invocations but returns a 403 Access Denied. The IAM role attached to the Lambda has lambda:InvokeFunction and the trust policy allows lambda.amazonaws.com.

  • Architect endpoint: https://lambda.us-east-1.amazonaws.com/...
  • Method: POST
  • Headers: Authorization: Bearer <sig4>
  • Status: 403

Is Genesys missing a specific scope in the request signature? Or do I need to add a resource policy on the Lambda itself?