We have upgraded the Splunk to latest 6.4.1. After upgrading to latest version, Splunk app for AWS is showing all the resources count as 0. We have used the same IAM credentials in our test account and we are able to see the information without any issues.
I'm currently on Splunk Enterprise 6.3.0 and Splunk App for AWS 4.2.1
Are you using the Splunk Enterprise appliance from the AWS Marketplace? If so, I'm ready to update mine so if you don't mind sharing how you updated your AMI I can give it a shot and see if I run into the same problem.
My issue got resolved after upgrading the splunk app for AWS to latest version. Our splunk servers are hosted in AWS but we are not using AWS marketplace AMI's. I have upgraded my Splunk cluster and forwaders to 6.4.1 without any issues.