Hello @Ale1911 and welcome to the Sonos Community!
I’d like to apologize to you and the rest of our users in this thread for the delay on my response.
Also my assistant has changed voice... without any reason.
The above makes me believe there’s been a change in your Google Assistant profile settings. You can find instructions by Google on the following page Change Google Assistant settings for both Android and iOS.
I would suggest you to follow the basic troubleshooting steps in our Google Assistant commands not working on Sonos support page.
If by doing so your issue is not resolved, please reach out to our Support team for some live troubleshooting.
I hope this helps.