You can ssh into an ec2 elastic instance by using the elasticbamboo.pk key that Bamboo setup. However, you login as the ec2-user not the bamboo user that the agent use to run the build.
The build files are located in the /home/bamboo user directory and the ec2-user does not have permission to it.
How do you login/su to the bamboo user so you can inspect the build files, logs, etc. for troubleshooting purpose?