What is an nbn battery?

Have you tried wiring one of your Sonos devices to your router with an Ethernet cable?

It’s the back up battery for my wifi 

I don’t understand why it would have had me lose all my Sonos . 
I haven’t tried the ethernet cable, I’m not sure I have one 

Huh. Never heard of an nbn internet device, much less an nbn battery. 
 

If you’re unable to find an Ethernet cable, you may want to call Sonos Support directly to discuss it.

When you speak directly to the phone folks, they have tools at their disposal that will allow them to give you advice specific to your network and Sonos system. But they may give you the same suggestion.