It is required that your private key files are NOT accessible by others. ubuntu code example
Example 1: It is required that your private key files are NOT accessible by others. This private key will be ignored.
# if you are using WSL then include sudo before the commands
sudo ssh ...
Example 2: private key is too open
chmod 600 ~/.ssh/id_rsa
Example 3: It is required that your private key files are NOT accessible by others ubuntu
chmod 400 {keyfile}.pem is what amazon instructed and it works.