You have generated a certificate file:
openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout test.key -out test.pem
After deploying the key, you try to ssh into the instance but get prompted for a password.
ssh -vvv -i test.pem <user>@<host>
This is an issue with an updated openssl version,
> openssl versionOpenSSL 1.0.1k 8 Jan 2015
This is a new version of openssl. The new version does not create the key with RSA at the begin and end. So you have to use a separate command to convert the key file to old version of ssh
openssl rsa -in test.key -out test_new.key
Once that is done, use the new file for ssh.
ssh -vv -i test_new.key <user>@<host>