Recurring Task Notification with datetime calculations (HVAC Filter Replacement Reminder)

In my automation for some reason it’s give me an error:

alias: "Notify: HVAC Filter"
description: ""
trigger:
  - platform: state
    entity_id: sensor.hvac_filter_days_left
    to: "0"
    id: Days Left HVAC
condition: []
action:
  - service: notify.mobile_app_sm_s918u
    data:
      message: Time to Replace an HVAC Filter
  - service: input_boolean.turn_off
    target:
      entity_id: input_boolean.hvac_filter_clean
    data: {}
mode: single
    - name: HVAC Filter Days Left
      unique_id: 1ef0d629-911a-4a18-96a1-f0503e77b119
      #friendly_name: 'HVAC Filter Days Left'
      state: >
        {% set hvac_filter_change_date = strptime(states('input_datetime.hvac_filter_date_last_changed'), '%Y-%m-%d %H:%M:%S') + timedelta(days=states('input_number.hvac_filter_days_until_old') | int) %}
        {{ (as_timestamp(hvac_filter_change_date) / 86400 - as_timestamp(now()) / 86400) | int  }}
      icon: mdi:clock-end
      unit_of_measurement: 'Days'