How to use Google speakers as audiosinks using Chromecast binding to make announcements?

I’m trying to use my Google speakers as audio sinks via the Chromecast binding to make announcements. I’m using VoiceRSS TSS. I am using Windows 11 Desktop, and openHAB 4.2.2 on the UI version. I’m very much a beginner, so apologies in advance.

I can’t tell if my problem is with the Google speakers not being recognised as audio sinks, an issue with the TTS VoiceRSS, or something else entirely. Any tips or ideas welcomed.

I have followed the VoiceRSS guide here and set it as default under Settings → Voice, and enGB_Nancy as the default voice. I did it originally with the UI and then again by editing the text files later. However, I wonder if it is working as it should because there is nothing in VoiceRSS → Cache? However, my API definitely works because this link works:

http://api.voicerss.org/?key=my API key here&hl=en-gb&src=Hello%20World!

I’m trying to set up a rule so there is an annoucement on a particular speaker at a particular time. If I go through the UI it doesn’t work, the speaker simply bleeps, but I notice the code it generates doesn’t make any reference to the TTS:

actions:
  - inputs: {}
    id: "2"
    configuration:
      volume: 100
      sink: chromecast:audio:xxxxxxx
      text: Take out the bins!
    type: media.SayAction

I don’t know if that means that VoiceRSS is not configured correctly, or if that the UI rules don’t ever work for Chromecast speakers.

After some googling, most people seem to use this command for their Chromecast annoucements, and multiple peple have reported it works on theirs.
This command returns no error and the speaker bleeps, but it still doesn’t announce anything, and there is nothing in the VoiceRSS cache.

say("Hello", "voicerss:enGB_Nancy", "chromecast:chromecast:xxxxxx")

I’ve tried different speakers, no luck. Any ideas as to what I might be missing? Or even suggestions how to figure out which part of it contains the error? I’ve spent days on this, thus the multiple edits, and I’m completely stuck. Please let me know if there’s anything I should add as well. Thanks in advance!