Verifica se o serviço de notificação esta habilitado para o aplicativo.

NotificationService.kt

// CRIAR SERVIÇO PARA INTERCEPTAR NOTIFICAÇES:
class NotificationService : android.service.notification.NotificationListenerService() {
    override fun onCreate() {
        super.onCreate()
    }
    override fun onNotificationPosted(sbn: StatusBarNotification) {
    }
    override fun onNotificationRemoved(sbn: StatusBarNotification) {
    }
}

NotificationService_Manifest.xml

<!-- DECLARAR NO MANIFEST -->
<service
    android:name=".services.NotificationService"
    android:label="@string/notification_label"
    android:permission="android.permission.BIND_NOTIFICATION_LISTENER_SERVICE">
    <intent-filter>
        <action android:name="android.service.notification.NotificationListenerService" />
    </intent-filter>
</service>

NotificationUtils.java

/**
 * Is Notification Service Enabled.
 * Verifies if the notification listener service is enabled.
 * Got it from: https://github.com/kpbird/NotificationListenerService-Example/blob/master/NLSExample/src/main/java/com/kpbird/nlsexample/NLService.java
 *
 * @return True if eanbled, false otherwise.
 */
private boolean isNotificationServiceEnabled(Context context) {
    String pkgName = context.getPackageName();
    final String flat = Settings.Secure.getString(context.getContentResolver(),
            ENABLED_NOTIFICATION_LISTENERS);
    if (!TextUtils.isEmpty(flat)) {
        final String[] names = flat.split(":");
        for (int i = 0; i < names.length; i++) {
            final ComponentName cn = ComponentName.unflattenFromString(names[i]);
            if (cn != null) {
                if (TextUtils.equals(pkgName, cn.getPackageName())) {
                    return true;
                }
            }
        }
    }
    return false;
}