Setting layer visibilty in custom QGIS 3.x application (C++ versus Python)

Question

In my QGIS application, I would like to be able to have a QDialog window pop upon clicking a toolbar icon which lists the layers set to the map canvas, and have QCheckBoxes that allow the user to show/hide layers if needed. I am trying to do so in a C++ application. I have a Python version which follows the answer given by Denis Rouzaud in the following example: Setting layer visibility in QGIS Python API?

Here is the custom slot I wrote which follows the API documentation:

void layerDisplay::setDisplay(QString &layerName, bool &isChecked)
{
    for ( QgsMapLayer *lay: qm0->layers() ) //qm0 is QgsMapCanvas
    {
        if ( layerName != lay->name() )
        {
            continue;
        } else
        {
            //pj0 is the QgsProject
            QgsLayerTreeNode *root = pj0->instance()->layerTreeRoot()->findLayer(lay->id());
            root->setItemVisibilityCheckedRecursive(isChecked);
            qm0->refresh();
            QList<QgsMapLayer* > lst = root->checkedLayers();
        if ( lst.isEmpty() )
        {
            cout &lt;&lt; &quot;Layer &quot; &lt;&lt; layerName.toStdString() &lt;&lt; &quot; is not checked&quot; &lt;&lt; endl;
        } else
        {
            for ( QgsMapLayer *lc: lst )
            {
                cout &lt;&lt; &quot;Layer &quot; &lt;&lt; lc-&gt;name().toStdString() &lt;&lt; &quot; is checked&quot; &lt;&lt; endl;
            }
        }
    }
}

}

and while the standard output tells me the layers have been checked or unchecked, the map canvas does not update; however the Python code works! If you need to see more code (eg the widget's header and mainwindow slot) I can update this question.