Binary_sensor value in notification

Hi,
i created an ios notification with a value as subtitle, but i did not get the value itself but the explitzit string i that i use.

- alias: Basemend Door Notification
  trigger:
    platform: state
    entity_id: binary_sensor.kellertuer_sensor
    to: 'on'
    for:
      minutes: '5'
  action:
    service: notify.iosgroup
    data:
      title: "Fenster / Tür offen"
      message: "Offen seit {{relative_time(states.binary_sensor.kellertuer_sensor.last_changed)}}"
      data:
        subtitle: "Kellertür offen!"
        push:
          thread-id: "basementdoor-open"

In other threads the configuration is exactly the same. Did i miss something?

Cheers.

you need to use data_template since you’re using a template in your message