Ubuntu – How to make nameservers based on the domain name in Amazon EC2

The first thing to do in this situation is to use the -v option to ssh, so you can see what types of authentication is tried and what the result is. Does that help enlighten the situation?

In your update to your question, you mention "on another local Ubuntu". Have you copied over the ssh private key to the other machine?

The specifics of how you do this will depend on who you registered the domain with, but you want to look into how to set the "glue" records for your domain.