Automation to notify when plug is On

Hello,
I have a smart plug and I would like to get a notification when it is on.
My automation:

alias: PLUG - notification
description: ''
trigger:
  - platform: state
    entity_id: switch.plug10
    to: 'On'
action:
  - service: notify.mobile_app_my_iphone
    data:
      title: notification
      message: Plug is on
mode: single

I cannot figure out why this is not working

Take a look in Dev Tools/states and find your switch.plug10.
There you will see that the state is on, not On.