Need help with attribute trigger for caldav calendar automation

Configuration
1

Hi,
I want to write an automation that triggers when the offset is reached of an event in a caldav calendar.
I can see in the dev tools that the calendar is set up correctly and the offset is parsed correctly.
Using the state changed event listener, I can observe the event where the offset attribute changes:

{
    "event_type": "state_changed",
    "data": {
        "entity_id": "calendar.familie",
        "old_state": {
            "entity_id": "calendar.familie",
            "state": "off",
            "attributes": {
                "message": "test calendar entry",
                "all_day": false,
                "start_time": "2022-02-18 11:35:00",
                "end_time": "2022-02-18 12:05:00",
                "location": null,
                "description": null,
                "offset_reached": false,
                "friendly_name": "Familie"
            },
            "last_changed": "2022-02-18T10:09:43.293974+00:00",
            "last_updated": "2022-02-18T10:29:44.038836+00:00",
            "context": {
                "id": "b5d8ef023c07360b9a612387c9352f42",
                "parent_id": null,
                "user_id": null
            }
        },
        "new_state": {
            "entity_id": "calendar.familie",
            "state": "off",
            "attributes": {
                "message": "test calendar entry",
                "all_day": false,
                "start_time": "2022-02-18 11:35:00",
                "end_time": "2022-02-18 12:05:00",
                "location": null,
                "description": null,
                "offset_reached": true,
                "friendly_name": "Familie"
            },
            "last_changed": "2022-02-18T10:09:43.293974+00:00",
            "last_updated": "2022-02-18T10:32:43.316665+00:00",
            "context": {
                "id": "2d8797edf3787369e8fd42217b33dd66",
                "parent_id": null,
                "user_id": null
            }
        }
    },
    "origin": "LOCAL",
    "time_fired": "2022-02-18T10:32:43.316665+00:00",
    "context": {
        "id": "2d8797edf3787369e8fd42217b33dd66",
        "parent_id": null,
        "user_id": null
    }
}

But the following automation (build according to Automation Trigger - Home Assistant) never triggers:

Automation with attribute trigger:

alias: 'Notify: Family calendar offset reached (Duplicate)'
description: ''
trigger:
  - platform: state
    entity_id: calendar.familie
    attribute: offset_reached
condition: []
action:
  - service: logbook.log
    data:
      name: Calendar Offset reached
      message: The calendar has reached the next offset
      entity_id: calendar.familie
mode: single

setting from and/or to to false/true does not change anything.

Any help is appreciated. Also any tips on how to debug this further.

2

This is a guess, you have omitted to: and since the state in the calendar is string "true" and not boolean true it does not trigger.
I suggest trying:

  - platform: state
    entity_id: calendar.familie
    attribute: offset_reached
    to: "true"

Edit:

Didn’t see this.
Was it like my suggestion above then you can discard this.