GreenDAO To many relations not adding rows to join class

Hello I'm using greenDAO To-Many relations as follows: An user can be listening to 0 or many audiobooks (audiolibro in code) so I have this in entity class.

@ToMany
@JoinEntity(entity = UsuarioAudiolibro.class,
            sourceProperty = "usuarioID",
            targetProperty = "audiolibroID"
            )
List<Audiolibro> audiolibros;

I'm using a testing class to load some test data as follows:

public class Prueba {
public static void datosPrueba(DaoSession session){
    session.getPersonaDao().deleteAll();
    session.getUsuarioDao().deleteAll();
    session.getAudiolibroDao().deleteAll();
    Persona pers = new Persona();
    // ... set persona data

    Persona pers2 = new Persona();
    // ... idem

    Persona pers3 = new Persona();
    // ... same

    // Here I persist Persona
    PersonaDao persDao = session.getPersonaDao();
    persDao.insertOrReplace(pers);
    persDao.insertOrReplace(pers2);
    persDao.insertOrReplace(pers3);

    //Create users 1-to many
    Usuario user = new Usuario();
    //sets data for user
    Usuario user2 = new Usuario();
    //sets data for another user
    Usuario user3 = new Usuario();
    //same again

    user.setPersona(pers);
    user2.setPersona(pers2);
    user3.setPersona(pers3);
    // persist usuario
    UsuarioDao userDao = session.getUsuarioDao();
    userDao.insertOrReplace(user);
    userDao.insertOrReplace(user2);
    userDao.insertOrReplace(user3);
    userDao.insertOrReplace(user4);


    //Create audiolibros

    Audiolibro audio = new Audiolibro();
    //... set audiolibro data

    Audiolibro audio2 = new Audiolibro();
    // ... set data

    Audiolibro audio3 = new Audiolibro();
    // ... set data

    //persist audiolibro
    AudiolibroDao audioDao = session.getAudiolibroDao();
    audioDao.insertOrReplace(audio);
    audioDao.insertOrReplace(audio2);
    audioDao.insertOrReplace(audio3);

    //add audiolibros to usuario
    List<Audiolibro> audiolibrosUser = user.getAudiolibros();
    audiolibrosUser.add(audio);
    audiolibrosUser.add(audio2);
    userDao.update(user);
    List<Audiolibro> audiolibrosUser2 = user2.getAudiolibros();
    audiolibrosUser2.add(audio2);
    audiolibrosUser2.add(audio3);
    userDao.update(user2);
    List<Audiolibro> audiolibrosUser3 = user3.getAudiolibros();
    audiolibrosUser3.add(audio3);
    audiolibrosUser3.add(audio);
    userDao.update(user3);
    }
}

After this the list of audilibros can be accessed here, but when I try to retrieve data from session in an activity the list seems empty. I tried reseting the list wit resetlist() in activity code but doesn't work. When I inspect the database there's not rows in the JoinTable.

What am I doing wrong?