Codeigniter Website Showing Blank Page in AWS Elastic Beanstalk

Unless you are moving it to an environment 100% like the one you tested, things like this happen. A blank page can mean several things such as Apache works, but it isn't being routed correctly or there is a PHP error and the php.ini is set to not show errors. Time to troubleshoot by looking at the access/error logs for Apache.

I'm assuming you set the DirectoryIndex appropriately?

That would be my guess. I use opsworks instead of EBS but I would check to see if you're launching in a production env that is suppressing errors.

Codeigniter is simply one of the tools you need to learn to be a successful developer. Always add more tools to your coding arsenal!