Notification not applied

I’m trying to apply a notification rule to services if they have a specific variable configured:

// Notification level 3: configured through 'notification_level' service var == 3
apply Notification "notification-level-3" to Service {
  import "mail-service-notification"
  user_groups = "notification-group-level-3"

  interval = 12h

  // Rewrite states if declared into service
  if (service.vars.notification_states) {
    states = service.vars.notification_states
  }

  assign where service.vars.notification_level == "3"
  //assign where host.vars.notification.mail
}

I have a service with notification_level = "3":

object Zone "www1.local.domain" {
  endpoints = [ "www1.local.domain" ]
  parent = "monitoring.local.domain"
}

object Endpoint "www1.local.domain" {
  host = "123.123.123.123"
}

object Host "www1.local.domain" {
  import "generic-host"
  address = "123.123.123.123"

  vars.os = "Windows"
  vars.distro = "Microsoft Windows Server 2019 Standard"


  vars.notification["mail"] = {
    groups = [ "icingaadmins" ]
  }

  vars.client_endpoint = name

  vars.http_vhosts["IIS HTTP Service"] = {
    http_uri = "/"
  }
  vars.http_vhosts["IIS Site www.mysite.com"] = {
    http_address = "123.123.123.124"
    http_vhost = "www.mysite.com"
    http_uri = "/"
    notification_level = 3
  }
}

I’m expecting that the IIS Site www.mysite.com check would have the notification-group-level-3 added to notification users, but it only has the default icingaadmins group:

Screenshot 2021-07-29 at 16.48.43

Could you help me to understand where I’m wrong please?

Thank you!