I assume you are using both voice assistants, each installed on separate Sonos devices, but can you kindly describe your setup in a little more detail. What Sonos devices are in use with each assistant and are they each installed in the same/different Sonos Household, in the same/different Sonos Account?
Which paid-subscription streaming music service(s) are you using as your default service in the Google Home & Amazon Alexa Apps?
Have you tried removing the Sonos ‘action’/‘skill’ from the Home app and have you tried removing the Sonos Skill from the Alexa App and then removed/reinstalled the voice assistant on their respective Sonos devices to setup the shared token with Google/Amazon again?