I am currently working on a POC trying to send files from my local on-premises server to AWS S3. It is giving me error unable to execute HTTP request: Network is unreacheable
Are you able to ping the S3 or access the S3 endpoint from you NiFi server ?
If your NiFi server is on private subnet with no EIP attached you need to create an VPC endpoint to your S3 service
If this you case follow this link :https://aws.amazon.com/blogs/aws/new-vpc-endpoint-for-amazon-s3/
Actually my nifi is on premises , anyways issue got fixed. need to provide proxy details like http url and port number in nifi. Its great tool which makes you to connect your on premises to cloud which you can send files. Right now i am working with smaller ones ,need to see how it behaves with Larger volumes