Having trouble logging into an AWS instance using an SSH key? I was too and when I finally figured out what the issue was I was kicking myself. Recently I was called to assist figuring out information about a clients AWS deployment for a project where the original developers were no longer available or answering questions. Most of the instances that I initially worked on had no issues once I was able to obtain the correct SSH key pem file from Amazon. When the project was closing down I was asked to assist backing things up and it appeared the SSH key was failing for two of the instances which also happened to be the oldest two instances (2 years old). Below I describe the error I was seeing via SSH as well as the easy resolution to the problem.