This tutorial was made on Saturday, 4th May 2019 using Unity 2018.3.14f1.
In my previous tutorial I described how to set up AWS S3 for Unity, this tutorial shows how to fix the broken S3 example from Amazon.
Download the zip from Amazon as shown in the steps from Set Up the AWS Mobile SDK for Unity: http://sdk-for-net.amazonwebservices.com/latest/aws-sdk-unity.zip
Use Unity 2018.3.14f1 because the latest Unity has a bug with AWS. The issue has been reported, please vote on it so that a fix is put in place and we can use the latest version of Unity: Android AWS SDK stopped working in Android Builds with Unity 2019.1.0a1 and up.