AWS ARN is Invalid while deploying API in API gateway. AWS ARN for integration contains invalid path

Question

I have been following this tutorial on Creating a REST API as an Amazon S3 proxy in API Gateway

https://docs.aws.amazon.com/apigateway/latest/developerguide/integrating-api-with-aws-services-s3.html

While Deploying the API I get this strange error- AWS ARN for integration contains invalid path

I have created the role using Cognito- Create new Identity pool which created two IAM roles for me one for handing the authenticated users and other to handle the unauthenticated users.

I am not sure why the deploy throws me error when I use the unauthenticated user IAM role ARN.

Can somebody help me if they have faced the issue earlier? Or perhaps a better resource to create the API

I am following the tutorial exactly.
This is what I did to create an IAM role

Created an IAM role Select trusted entity- AWS Service

Use case- API gateway

Permissions Added -AmazonS3FullAccess, AmazonAPIGatewayPushToCloudWatchLogs

For creating the API I copied the exact same procedure except for two steps( or may be one)-

1. I chose region as ap-south-1 while creating get method at root level

2. For action type I chose path override as mentioned in tutorial but I path the path as blank. I am not sure if this is correct.

At last as given in tutorial I was expecting the results with timestamp and content type as mentioned in tutorial but I get this AWS ARN for integration in invalid error instead