The car communicates with Nissan's servers through the AT&T cellular network so you need a good AT&T signal where the car is parked for notifications to work. Try enabling email notifications in addition to text messages. If you get email notifications, then the problem could be with your cellular provider not delivering your messages or the Nissan servers not sending the text messages. Try resetting all of your notification parameters in your EV Connect profile to see if that helps.
Silver LEAF 2011 SL rear ended (totaled) by in-attentive driver 1/4/2015 at 50,422 miles
Silver LEAF 2015 SL purchased 2/7/2015