Labels do not appear in QChartView

[Samuel Ives]

I'm trying to generate a sales report that shows the amount of sales of the day on a particular day of the month in the chart.

RelatorioDeVendas::RelatorioDeVendas(QWidget *parent) :
    QDialog(parent),
    ui(new Ui::RelatorioDeVendas)
{
    ui->setupUi(this);

    QChart *chartMensal = new QChart();
    QLineSeries *seriesMensal = new QLineSeries();

    Relatorios::vendasMensais(seriesMensal, chartMensal);

    chartMensal->addSeries(seriesMensal);
    chartMensal->setTitle("Vendas do mês");
    chartMensal->legend()->setVisible(false);

    ui->chartViewMensal->setRenderHint(QPainter::Antialiasing);
    ui->chartViewMensal->setChart(chartMensal);

}

void Relatorios::vendasMensais(QLineSeries *series, QChart *chart)
{

   QSqlDatabase db = Database::database();

   QSqlQuery q(db);
   q.prepare("SELECT COUNT(id), feita_em FROM vendas WHERE YEAR(feita_em) = :ano AND MONTH(feita_em) = :mes GROUP BY DAY(feita_em)");
   q.bindValue(":ano", QDate::currentDate().year());
   q.bindValue(":mes", QDate::currentDate().month());

   if(!q.exec()){
       qCritical() << "Falha ao realizar a consulta: " << q.lastError().text();
       return;
   }

   QCategoryAxis *xAxis = new QCategoryAxis();

   while(q.next()){

       QDateTime data = QDateTime::fromString(q.value(1).toString(), "yyyy-MM-ddThh:mm:ss.z");

       xAxis->append(QString::number(data.date().day()), data.date().day());
       series->append(data.date().day(), q.value(0).toInt());

   }

   chart->createDefaultAxes();
   chart->addAxis(xAxis, Qt::AlignBottom);

}

But the days do not appear in the graph even using QCategoryAxis