Check on your smartphone that notifications for the Home + Security App are enabled
Note: Some Android manufacturers limit the functionality of background apps to maximize battery life. This may prevent you from receiving Home + Security applications
By way of example, in this link you can find procedures https://dontkillmyapp.com/ (Legrand Netatmo Bticino is not responsible for the contents of this site)
Finally, remember that even a poor Wi-Fi signal can cause problems with notifications.