Automation to play MP3 on a group of VPEs

I have several VPEs throughout the house. I have an MP3 file that I want to play on all of them at the same time. It is a burglar alarm sound and I’m setting up alarmo. Until I can get an actual siren set up, I want to play this MP3 file on them all.

Here’s what I’ve currently got set up. Every time I click on Run Action, it says “Action ran successfully”. But no sound came out of any of them. The volume is fine as just before running this test, I had it run the same mp3 on the two VPEs that are nearest to me and I heard them just fine.

action: media_player.play_media
metadata: {}
data:
  media_content_id: /media/burglar_alarm.mp3
  media_content_type: music
target:
  entity_id: media_player.all_vpes

Definition of All VPEs:

I added this action to the automation. It makes an announcement on the same All VPEs group – it works fine.

action: tts.cloud_say
metadata: {}
data:
  cache: false
  entity_id: media_player.all_vpes
  message: The Garage Door has been opened!

Anyone have any ideas?