ASP NET Core AWS No RegionEndpoint or ServiceURL configured when deployed to Heroku
Looks like you are building a ASP.NET Core application which doesn't use web.config other then some IIS integration. You should either put the region in the appsettings.json file like shown here https://aws.amazon.com/blogs/developer/configuring-aws-sdk-with-net-core/ or set the environment variable AWS_REGION to your desired region.