Samsung Q Series Soundbar Not Playing Audio Notifications

Hi all, I’ve been trying to get an audio notification to play via a Samsung Q Series soundbar. I recall there being these apis (which seem to have disappeared from the SmartThings API documentation).
https://api.smartthings.com/v1/services/tts/playtext
https://api.smartthings.com/v1/services/tts/
I have been able to generate an MP3 via the /tts endpoint, and have been able to send the notification to the device, which gives me a response of:

{
    "message": "Audio played on device successfully"
}

However, no sound is playing from the soundbar itself.

I have also tried calling the audioNotification command directly using the endpoint:

https://api.smartthings.com/v1/devices/{deviceId}/commands
with the following input

{
  "commands": [
    {
      "component": "main",
      "capability": "audioNotification",
      "command": "playTrack",
      "arguments": [
          "https://dm0v67zzwhdtd.cloudfront.net/polly/053409ce0b019423f118c312d2f04ccd3a1bbd6af92931f603b6b37f557460f0.mp3",
            100
      ]
    }
  ]
}

which is also not working, even though it is responding with a result of “Accepted”.

Finally, I have tried directly calling the command directly in the smartThings dashboard, which also isn’t playing anything.

The only way I have managed to get a notification to play is directly via creating a Routine in the smartThings app, but this isn’t what I am trying to accomplish.

Is there something that I am missing here?