Connect to Google Cloud Platform VM with Jsch

Question

I'm trying to connect to Google Cloud VM from Spring Boot app. This is the first time I'm doing something like that, but I get an Auth fail exception no matter what I'm trying.

This is my code:

@Component
@AllArgsConstructor
@NoArgsConstructor
public class SftpDownloader {


            String SFTPHOST = "MY-SERVER-IP";
            int SFTPPORT = 22;
            String SFTPUSER = "yarin";
            String privateKey = "/Users/yarin/.ssh/gcpdash";
            String SFTPWORKINGDIR = "/";
            JSch jSch = new JSch();
            Session session = null;
            Channel channel = null;
            ChannelSftp channelSftp = null;

            public void downloadFromSftp (){
            try {
                jSch.addIdentity(privateKey);
                System.out.println("Private Key Added.");
                session = jSch.getSession(SFTPUSER, SFTPHOST, SFTPPORT);
                session.setPassword("");
                System.out.println("session created.");
                java.util.Properties config = new java.util.Properties();
                config.put("StrictHostKeyChecking", "no");

                session.setConfig(config);
                session.connect();
                channel = session.openChannel("sftp");
                channel.connect();
                System.out.println("shell channel connected....");
                channelSftp = (ChannelSftp) channel;
                channelSftp.cd(SFTPWORKINGDIR);
                System.out.println("Changed the directory...");
            } catch (JSchException e) {
                e.printStackTrace();
            } catch (SftpException e) {
                e.printStackTrace();
            } finally {
                if (channelSftp != null) {
                    channelSftp.disconnect();
                    channelSftp.exit();
                }
                if (channel != null)
                    channel.disconnect();
                if (session != null)
                    session.disconnect();
            }
        }
    }

I am able to connect to the GCP VM with the same key from "FileZilla", So I think everything is ok from GCP side.