Hello LeonardoZ,
Welcome to Apple Support Communities! I understand your Voice Control disables itself on your MacBook Pro. I'm happy to assist you with this.
Let's enable Voice Control again. Once you've enabled this setting, watch the "Enable Voice Control" checkbox for 15 seconds, to see if the checkmark goes away:
Use Voice Control on your Mac
Next, create a new user account. This will help isolate the cause of this issue:
How to test an issue in another user account on your Mac
In the new user account, enable Voice Control and watch again to see if the checkmark goes away.
If the issue persists in the new user account, contact Apple Support:
Contact Apple for support and service
Best Regards.