Are you using the event name, or the event code in your sketch when you attempt to trigger the notification?
How are your notification settings configured?
Have you taken any precautions in your code to prevent multiple consecutive notifications being sent, and your notification quota being exceeded?
What does your event log show?
I wrote this guide a while ago, and although the Blynk UI and some of the defaults have now changed, the basic principals are the same….
Pete.