Script Triggers Via GUI But Fails to Trigger as Part of Automation

Configuration
1

I have the following script that successfully triggers via the HA GUI:

mute_wait_unmute_lounge:
    sequence: 
    - service: switch.turn_on
      entity_id: switch.soundbar_mute
    - delay:
        seconds: 3.5
    - service: switch.turn_off
      entity_id: switch.soundbar_mute

However when I include it as part of the following automation, it fails to trigger:

# sessionStarted
  - alias: "sessionStarted music_mode lounge (MUTE WAIT UNMUTE)"
    trigger:
      platform: mqtt
      topic: hermes/dialogueManager/sessionStarted
    condition:
    - condition: template
      value_template: "{{ trigger.payload_json['siteId'] == 'lounge' }}"
    - condition: template
      value_template: "{{ trigger.payload_json['customData'] == 'music_mode' }}"
    # SOUNDBAR MUST BE ON MUSIC SOURCE FOR THIS TRIGGER TO INITIATE
    - condition: template
      value_template: "{{ is_state('switch.soundbar_power', 'on') }}"
    - condition: template
      value_template: "{{ is_state('switch.soundbar_music', 'on') }}"
    action:
      # MUTE FOR 3.5 SECS SO USER CAN SAY COMMAND THEN UNMUTE SO THAT THE MUSIC CAN BE HEARD
      service: script.mute_wait_unmute_lounge

When I check via the HA GUI, the conditions required for the automation to work are true but the script fails to execute.

Does anyone have any idea what I am doing wrong?

Thanks

2

What is the payload published to the topic?