Is the Github SSH tutorial correctly done?

According to this tutorial, I am sure I have successfully configure SSH. But why am I do still getting this error Permission Denied (publickey) when connecting to gerrit.LibreOffice.org? Can I use the same account ID for both Github.com in Gerrit?

Generating SSH Key If you have decided not to use the recommended HTTPS method, we can use SSH keys to establish a secure connection between your computer and GitHub. The steps below will walk you through generating an SSH key and then adding the public key to your GitHub account.