File Sensors not visible in States tab

I have the following set up:

notify:
  - platform: file
    name: Energy Midnight
    filename: /config/readings/Energy.txt

shell_command:
  delete_energy: 'rm /config/readings/Energy.txt'


sensors:
  - platform: file
    name: 'Import Midnight'
    file_path: /config/readings/Energy.txt
    value_template: '{{value_json.Import}}'
  - platform: file
    name: 'Export Midnight'
    file_path: /config/readings/Energy.txt
    value_template: '{{value_json.Export}}'
  - platform: file
    name: 'Generate Midnight'
    file_path: /config/readings/Energy.txt
    value_template: '{{value_json.Generate}}'
    
    
automation:
  - alias: Energy Readings 
    id: '1524401320302'
    trigger:
    - at: 00:00:00
      platform: time
    action:
    - service: shell_command.delete_energy
    - service: notify.energy_midnight
      data_template: 
        message: >-
          { "Import" : "{{states.sensor.grid_import_active_energy.state}}",
          "Export" : "{{states.sensor.grid_export_active_energy.state}}",
          "Generate" : "{{states.sensor.solar_import_active_energy.state}}" }

The automation produces the following text file at midnight:

 Home Assistant notifications (Log started: 2018-04-29T17:36:21.386964+00:00)
 --------------------------------------------------------------------------------
 { "Import" : "36557.53", "Export" : "10348.46", "Generate" : "21467.02" }

I have created sensors to read these values when required.

The problem is that these sensors are not visible in the States tab. Tried to look at the docs but could not spot what I am doing wrong.

If anyone can please heeeelp!!

Thank you.

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