WallPanel Audio problem

I’ve moved over to WallPane from Fully Kiosk as I found that too slow when rendering graphs.

I’m trying to use the audio command and not hearing anything.
I have an audio file on a network drive with the path

192.168.x.y/Public/Media/hourlychimebeg.mp3

When I type this in Chrome it plays the clip.
When I use HA Developer Tool/Actions to send the URL as part of an audio command to Wallpanel, I get nothing. No indication of an error in HA nor the panel itself.
The Topic is

wallpanel/mywallpanel/command

and the Payload

{"audio":"file://192.168.x.y/Public/Media/hourlychimebeg.mp3"}

I’ve tried it withoiut the file:// prefix and with http://. They don’t work either.
The volume is set to 80%.
If I send the payload

{"speak":"hello"}

that works fine.

What am I missing?

Edit:

I randomly looked for an audio clip on the net and came across this url of a sci fi space laser firing…

https://codeskulptor-demos.commondatastorage.googleapis.com/GalaxyInvaders/alien_shoot.wav

When I use this in the payload, it works! Still don’t see what I’m missing though.