The best way to see if products are “registered” to you is to go to www.Sonos.com, and log in. Go to My account, then System, and you’ll see what has been associated with your account. This process is automatic, when you add a factory new device to your system. Adding a previously registered device that has not been factory reset will not trigger this.
If you set up the speakers on your system using the Sonos app, they are automatically “registered” in your Sonos account.
To see all of your products, log in to the main Sonos website and go to “My Account” and select “System”.