If you have already tried:

Powering off everything. Your router/network, speakers and phone. Wait 5 minutes. Starting with the router/network, power it on and allow it to fully boot. Then starting with a single Sonos speaker, power it on. Repeat this for each speaker, then your phone. Connect to your system and try the update again.

If the update still doesn’t complete, waiting for level 2 support may be your best bet.

I have connected my router to a VPN in Australia (my region), still get the same error, yet when I connect to a VPN server located in Los Angeles, it works. Rules out my network. Why?

Great question, I don’t know. Most VPNs block outside connections, such as the speakers which attempt to your router while your PC is connected, but that doesn’t explain why LA works, and Australia doesn’t. 

I would recommend that you submit a system diagnostic, twice, once with the LA connection, annd with the Australia failure,  and call Sonos Support to discuss it. Don’t post the resulting diagnostic number here, they get sensitive about GDPR.

There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.

When you speak directly to the Support staff, they have tools at their disposal that will allow them to give you advice specific to your network and Sonos system.

I was scheduled to have a 2nd level support call, however nobody contacted me and I’ve just called back. I’m less than impressed.

Errors starting 1xxx can often be solved by installing the Sonos desktop app for either Windows or Mac (downloadable directly from the Sonos website) and checking for system updates, and then updating from there. 

ok, I’ve managed to have a support session with Sonos, I can confirm that the Sonos Five has an issue with DNS, pinging the update server directly from the sonos device returns “Bad Address” yet pinging the same server outside of this returns a response. 

Sure sounds like some sort of port blocking event. Based on your mention of a VPN, I’d suggest, without any hard data like that which Sonos has, a result of that. But hard to tell externally. 

They do provide a tools portal from the device itself. Open your webpage, put in the IP and the port like this <IP>:1400/tools, there you can perform a ping, traceroute and nslookup, if I’m not connected to a US based VPN, I get bad address, however when I connect to a VPN say in LA, it succeeds. In my view it rules out my router and my network.