Need help with train delay script

Hi, i would try to make an train delay script with the dutch railway NS integration. when i execute the script i get an error message:ValueError: Template error: strptime got invalid input 'unknown' when rendering template '{{ (strptime(actual_time, "%H:%M") - strptime(planned_time, "%H:%M")).total_seconds() / 60 }}' but no default was specified

i have tried to add now() to the actual_time and planned_time but with no succes can somebody help me to made this script work when there is an train delay? the default message is working correct.
here is my script:

alias: Train delay
sequence:
  - variables:
      planned_time: >-
        {{ states("sensor.train",
        "departure_time_planned") }}
      actual_time: >-
        {{ states("sensor.train",
        "departure_time_actual") }}
      delay: >-
        {{ (strptime(actual_time, "%H:%M") - strptime(planned_time,
        "%H:%M")).total_seconds() / 60 }}
  - choose:
      - conditions: "{{ delay > 0 }}"
        sequence:
          - service: notify.mobile_app_iphone_van_willem
            data:
              message: The train is delayed by {{ delay }} minutes
              data:
                push:
                  sound:
                    name: default
                    critical: 1
                    volume: 1
          - if:
              - condition: state
                entity_id: person.willem
                state: Thuis
            then:
              - service: sonos.snapshot
                data:
                  with_group: true
                  entity_id: media_player.studeerkamer
              - service: media_player.volume_set
                data:
                  volume_level: 0.11
                target:
                  entity_id: media_player.studeerkamer
              - service: tts.cloud_say
                data:
                  cache: false
                  entity_id: media_player.studeerkamer
                  language: nl-NL
                  message: >-
                    De Trein heeft een vertraging van {{states('delay')}}
                    minuten
              - delay:
                  hours: 0
                  minutes: 0
                  seconds: 1
                  milliseconds: 0
          - service: sonos.restore
            data:
              with_group: true
              entity_id: media_player.studeerkamer
    default:
      - service: notify.mobile_app_iphone_van_willem
        data:
          message: The train is on time and leaves on {{ actual_time }}
mode: single

shouldn’t this:

sequence:
  - variables:
      planned_time: >-
        {{ states("sensor.train","departure_time_planned") }}

be

{{ state_attr("sensor.train","departure_time_planned") }}

and same for actual_time?

Also, what happens when you put it into developer toolstemplate?

I have made an automation that is working.

alias: Notify when train is late
description: Notify when the train has a delay and going
trigger:
  - platform: time
    at: "07:10:00"
  - platform: time
    at: "07:18:00"
condition:
  - condition: template
    value_template: >-
      {% set planned_time =
      state_attr('sensor.train_07h24m_train',
      'departure_time_planned') %}
 
      {% set actual_time =
      state_attr('sensor.train_07h24m_train',
      'departure_time_actual') %}
 
      {% if planned_time != "unknown" and actual_time != "unknown" %}
        {% set planned_time_obj = strptime(planned_time, "%H:%M") %}
        {% set actual_time_obj = strptime(actual_time, "%H:%M") %}
        {% if (actual_time_obj - planned_time_obj).seconds == 0 %}
          True
        {% else %}
          False
        {% endif %}
      {% else %}
        False
      {% endif %}
action:
  - choose:
      - conditions: "{{ False }}"
        sequence:
          - choose:
              - conditions:
                  - condition: template
                    value_template: >
                      variables:
 
                      {% set planned_time =
                      state_attr('sensor.train',
                      'departure_time_planned') %}
 
                      {% set actual_time =
                      state_attr('sensor.train',
                      'departure_time_actual') %}
 
                      {% if planned_time != "unknown" and actual_time !=
                      "unknown" %}
                        {% set planned_time_obj = strptime(planned_time, "%H:%M") %}
                        {% set actual_time_obj = strptime(actual_time, "%H:%M") %}
                        {% if (actual_time_obj - planned_time_obj).seconds == 0 %}
                          True
                        {% else %}
                          False
                        {% endif %}
                      {% else %}
                        False
                      {% endif %}
                sequence:
                  - variables:
                      planned_time: >-
                        {{
                        states("sensor.train_07h24m_train",
                        "departure_time_planned") }}
                      actual_time: >-
                        {{
                        states("sensor.train_07h24m_train",
                        "departure_time_actual") }}
                      delay: >-
                        {{ (strptime(actual_time, "%H:%M") -
                        strptime(planned_time, "%H:%M")).total_seconds() / 60 }}
                  - service: tts.cloud_say
                    data:
                      cache: false
                      language: nl-NL
                      entity_id: media_player.studeerkamer
                      message: De Trein heeft een vertraging van {{ delay }} minuten.
      - conditions: []
        sequence:
          - service: notify.mobile_app_iphone
            data:
              message: "  The train is on time and leaves on {{ states(\"sensor.train_07h24m_train\",     \"departure_time_actual\") }}"
mode: restart