I had a similar issue with my notifications not working properly after installing an application (Onovo) and issue was resolved upon removal of the application. While you may not have installed such application, I recommend removing any 3rd applications recently installed and then test. Notification issues are often caused by third applications installed on your phone. Keep us posted.
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make sure your switch on the side of your iphone is not to sound mode thats may be the problem. I fliped the switch and did not know one time and I was like what is going on and I noticed I fliped the switch
hope this helps NON vzw employee just a custmore