Cannot log in to phpMyAdmin when trying to connect to remote Amazon RDS

I have a php application running on Amazon Elastic Beanstalk running on their Linux Web Server OS. and a mysql database using Amazon RDS.

I can run a php script on the application that accesses the database and returns data, so I don't believe I have an issue with the database firewall.

I've installed phpMyAdmin on the server running the application, and have edited the config files so that I can now access the phpMyAdmin login page.

But when trying to log in (With the same credentials used in the application script that can access the database) I am given error: #2002 Cannot log in to the MySQL server.

I have tried looking at 6 or so different suggestions from other threads around about but none have helped. I have even allowed access for all traffic from any ip temporarily in the firewall security group, to rule out this as a cause.

Any ideas what this error is being caused by?