Login button is 'ghosted' in facebook login for android

I have the following code for the facebook login in an android Fragment:

    loginButton = (LoginButton) fragment.findViewById(R.id.login_button);
    loginButton.setReadPermissions("user_friends");
    // If using in a fragment
    loginButton.setFragment(this);
    // Other app specific specialization

    // Callback registration
    loginButton.registerCallback(C.callbackManager, new FacebookCallback<LoginResult>() {
        @Override
        public void onSuccess(LoginResult loginResult) {

            Log.wtf("onSuccess",loginResult.toString());

        }

        @Override
        public void onCancel() {

            Log.wtf("onCancel","");
        }

        @Override
        public void onError(FacebookException exception) {
            Log.wtf("onError",exception.toString());
        }
    });

The login button appears and when I click it a pop up appears asking for the login. I can enter the email and password but the button to send the credentials to facebook's servers does not function, not even click.

Sometimes I get these errors when the first menu (where the user is asked the credentials) doesn't open (happens frequently):

04-18 17:36:12.936    1607-1607/ E/ActivityThread﹕ Failed to find provider info for com.facebook.katana.provider.PlatformProvider
04-18 17:36:12.936    1607-1607/ E/ActivityThread﹕ Failed to find provider info for com.facebook.wakizashi.provider.PlatformProvider