When an app is upgraded, force stopped or data-cleared, Android system automatically removes all its active notifications immediately. This may be fine for most regular apps, but too bad for Nevolution since it actually hosts evolved notifications for other apps.
To avoid the potential loss of important notifications, you are suggested to install this Entension Pack, which serves as a safe harbor for all your evolved notifications. Then no matter what happens to Nevolution, they are always safe (except in rare extreme cases).
In case you can't install the Extension Pack via Google Play Store or find it in your favorite app store.