What music service are you using (is it a free, or subscription service)? Have you installed that service in both the Sonos App and the Google Home. Have you installed the Sonos action/skill for use by the assistant, assuming it’s available in your country of residence?

I have tried both Apple music and a free radio service.

Free services don’t work, but for supported music subscription services, perhaps see these support links to setup the Assistant with your speakers:

• https://support.sonos.com/en-us/article/set-up-the-google-assistant-with-a-voice-enabled-sonos-product
• https://support.sonos.com/en-us/article/set-up-a-google-assistant-device-to-control-sonos
• https://support.sonos.com/en-us/article/google-assistant-commands-not-working-on-sonos
• https://support.sonos.com/en-us/article/google-assistant-availability-on-sonos