Architect Data Action returns 403 when invoking Lambda via IAM role

Could someone clarify why the Architect Data Action consistently returns a 403 Forbidden error when attempting to invoke a specific Lambda function via an IAM role? The Angular service in the Genesys Cloud Premium App framework successfully triggers the flow, but the backend integration fails at the execution step.

  • Genesys Cloud Region: US-EAST
  • Architect Data Action Type: Invoke AWS Lambda
  • IAM Role: Attached to the Genesys Cloud service principal with lambda:InvokeFunction permission

The JSON response payload contains the following error structure:

{
 "error": "AccessDeniedException",
 "message": "User: arn:aws:sts::123456789012:assumed-role/GC-Integration-Role/... is not authorized to perform: lambda:InvokeFunction on resource: arn:aws:lambda:us-east-1:123456789012:function:MyTargetFunction"
}

The IAM policy explicitly allows this action. Is there a specific resource ARN format required in the Architect configuration?