There could be several reasons, why the push notifications are not working. However, the most common reason is that people have simply disabled notifications in the iPhone settings.

1. Go to your iPhone settings and click on "notifications".
2. Tap on mysms to check, if the option "Notifications Center" is on. It’s possible to choose whether you would like to receive notifications as banner or alerts. In addition, you can activate the badge app icon (red icon with number of new messages), the sound notification and the view in lock screen.
3. Now open the mysms app on your iPhone to receive push notifications again.