Can't connect to corporate machine with SSH JCraft JSch

Question

I've got a problem with connecting to corporate machine with SSH using JCraft JSch.

public static void main(String[] args) throws JSchException {
    JSch jSch = new JSch();
    String username = "username";
    String host = "host";
    int port = 22;

    jSch.addIdentity("Path\\to\\key\\file");
    jSch.setKnownHosts("known_hosts");

    /* In known_hosts file, I've got Host IP, and public key,
    the same that's on server
                                                             */
    Session session = jSch.getSession(username,host,port);

    Properties config = new Properties();
    config.put("StrictHostKeyChecking","yes");
    session.setConfig(config);

    session.connect(5000);


}

That's my code, after running it, there is an error: HostKey has been changed: [host adress], if i change StrictHostKeyChecking to no, another error appears: Auth fail.

I can connect to that machine via PuTTy or WinSCP, and I dont need to use tunneling. Also the key format is right(I made that mistake allready). When I connect to the machine via PuTTy, I need to pick the right machine(there are 5), and each of them has their own key pair, and the main connection to the "menu", has also it's own key pair, it's CAPI key.

Does anyone had something like that before? Also I made a forwarding port, and tried to connect with that, but I'm not sure how it works. Can anyone tell me how to do the port forwarding, or maybe somebody has another idea.

Thanks in advice