Strophe.js not sending iq

Question

I tried to create an Ionic 3 mobile chat. My code looks like this:

onRoster(a) {
    console.log("onRoster");

    return true;
}

onRosterChanged(a) {
    console.log("onRosterChanged");

    return true;
}

onPresence(a) {
    console.log("onPresence");

    return true;
}

onMessage(a) {
    console.log("onMessage");

    return true;
}

login(jid, sid, rid) {
    console.log("chat login");

    if(!this.chat) {
        console.log('creo connessione chat');
        this.chat = new Strophe.Connection(Configurazione.chatUrl);
    }

    let chatObj = this;
    //this.chat.connect(username + "@" + Configurazione.chatHost, password, chatObj.verificaConnessioneXMPP);
    this.chat.attach(jid, sid, rid, chatObj.verificaConnessioneXMPP)
}

verificaConnessioneXMPP(stato) {
    let chatObj = this;

    switch(stato) {
        case Strophe.Status.ATTACHED:
        case Strophe.Status.CONNECTED:
            console.log("logged");
            let iq = $iq({type: 'get'}).c('query', {xmlns: 'jabber:iq:roster'});
            console.log(iq);
            console.log("send iq");
            this.chat.sendIQ(iq, function(iq) { chatObj.onRoster(iq); }, function() { chatObj.onRoster(0); }, 1000);
            this.chat.addHandler(chatObj.onRosterChanged, "jabber:iq:roster", "iq", "set");
            this.chat.addHandler(chatObj.onMessage, null, "message", "chat");
            break;

        case Strophe.Status.DISCONNECTED:
            console.log("not logged");
            break;

        default:
            console.log("Altro stato: " + stato);
            break;
    }

    return true;
}

I can login to my XMPP server but I can't send IQ (this.chat.sendIQ), my callback function is never called. What's the problem? I can't find out