Network monitor is not always working

I don't know if it is a bug, but I can see that disabling the network interface or the wifi on mobile, no network event is received.
Also when I physically unplug/plug the cable, not all the time I trigger the app (using QtCreator) I receive qDebug info about this.
I attached a sample code that is not working disabling the network in the settings and launching in QtCreator sometimes is working sometimes not (removing physically the cable)