Application logs in, but redirects back to login

Question

I have a piece of code that do not work, and I cannot understand why. As the subject says, it logs in to Twitter, but redirects back to the sign in button. setupTimeline(); is never executed.

I am using twitter4j library, it is at the latest version, 4.0.7.

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    // Get the preferences for the app.
    tweetzPrefs = getSharedPreferences("TweetzPrefs", 0);
    // Find out if the user preferences are set.
    if (tweetzPrefs.getString("user_token", null) == null) {
        // No user preferences so prompt to sign in.
        setContentView(R.layout.activity_main);
        // Get a twitter instance for authentication.
        tweetzTwitter = new TwitterFactory().getInstance();
        // Pass developer key and secret.
        tweetzTwitter.setOAuthConsumer(TWIT_KEY, TWIT_SECRET);
        // Try to get request token.
        try {
            new Thread(new Runnable() {
                @Override
                public void run() {
                    try {
                        // Get authentication request token.
                        tweetzRequestToken = tweetzTwitter.getOAuthRequestToken(TWIT_URL);
                        Log.e(LOG_TAG, "Are we there Yeti?");
                    } catch (TwitterException e) {
                        e.printStackTrace();
                        Log.e(LOG_TAG, "TwitterException: " + e.getMessage());
                    }
                    if (tweetzRequestToken == null) {
                        Log.e(LOG_TAG, "tweetzRequestToken == null.");
                    }
                }
            }).start();
            // Get authentication request token.
            // tweetzRequestToken = tweetzTwitter.getOAuthRequestToken(TWIT_URL);
        } catch (Exception e) {
            e.printStackTrace();
            Log.e(LOG_TAG, "Exception: " + e.getMessage());
        }
        // Setup button for click listener.
        Button signIn = (Button) findViewById(R.id.signin);
        signIn.setOnClickListener(this);
    } else {
        // User preferences are set, get timeline.
        setupTimeline();
    }
}

Any ideas anyone?

Regards.