Ansible dynamic inventory, AWS and ec2_dns_name

Using the ec2.py script, I am trying to select an AWS machine by ec2_dns_name. It always seems to not match:

e$ ansible -i ./ec2.py ec2-34-192-103-30.compute-1.amazonaws.com -m ping
[WARNING]: No hosts matched, nothing to do

The output from the ec2.py script regarding the DNS name is this:

“ec2_public_dns_name”: “ec2-34-192-103-30.compute-1.amazonaws.com”,

I can use the script to connect to machines by IP address, region and tag name so I know the basic infrastructure is working (SSH, AWS keys, IAM rights, etc.). I have looked in the ec2.ini file and played with the settings for destination_variable. A setting of “public_dns” makes the most sense, since I am accessing the machine via that way.

I have looked at these both the Ansible docs for AWS and the AWS docs for Ansible:

http://docs.ansible.com/ansible/guide_aws.html

https://aws.amazon.com/blogs/apn/getting-started-with-ansible-and-dynamic-amazon-ec2-inventory-management/

Where can I look/what can I run to troubleshoot this? What am I doing wrong?

Thanks!