Sonos systems default to using DHCP for their IP address. This can cause issues with automation systems as the speakers can change IP for a number of reason and stop responding to command from the gateway. To prevent this issue you should ensure that your Sonos speakers have a static IP assigned using DHCP reservations in your router. Refer to your router manual for directions on how to add reservations.
Once the reservations are configured and the speakers rebooted (if the reserved address is different to the current address), follow the steps in the device wizard to add you Sonos speakers to the Nero system.