WordPress still requires FTP information

Guess it needs to be said first – it is a bad idea in general to just let anyone that succeeded to trick you into uploading his PHP onto your server to actually be able to write to your code directories. It is double problematic if you let him access to your root credentials and write to anywhere on your server.

That said, it sounds like you just don’t have an FTP server installed on your server. SFTP is different from FTP and being able to access via one do not ensure access with the other.

You should login to your server, run an FTP command with the credentials you put in the wp-config to first make sure you can connect and access the relevant directories. Once you can properly connect woth the FTP command on your server you can use the same credentials in your config.