Normally the surrounds and Sub connect on a dedicated wifi connection to the Arc. Make sure wifi is enabled on all the speakers - don’t use Ethernet cables. Power down all of them (and any other Sonos devices); then restart your router. When it’s fully started, with wifi running, power up the Arc. When it’s running, start the surrounds and then the Sub. Then start any other devices   That eliminates any possible ip address conflicts. 

Connection issues are common with Vodafone routers when using Wi-Fi.

Wiring the Arc by ethernet to the router is normally the recommended course of action.

If you wire your Arc your Ray should then connect to it over Sonosnet avoiding the iffy wifi.

Sonos does not get along well with the Speedport router from Vodafone. I’d recommend getting in touch with the support team.

Most likely to be told to wire the Arc as recent Vodafone threads have all confirmed their system works in a wired setup.

Very little point having a user community when the best answer is given to whoever posts contacting Sonos support.

If there is a better answer than the best answer, then the best answer is not better than the best. 

Seriously - can the ‘report’ function be used to flag an incorrect best answer?

Do Vodafone even supply Speedport routers in the UK?

ARRIS were manufacturers for the Hub 4 and Sagemcom the Hub 5

Hi ​@craigski & ​@Mr. T 

After consulting internal documentation, I saw no advice for wiring to ethernet for Vodafone routers as a workaround for the stated issue.

The documentation is not always up-to-date or indeed in possession of all the answers, of course, so if ​@77nill comes back and confirms that ethernet-wiring the Arc to the router fixed the issue, I will be happy to change the marked Best Answer to one that suggests that course of action.

If wiring to ethernet does not help, support should be contacted.

I hope this helps.

Assuming is Ultra Hub, its Technicolour router:

https://www.vantiva.com/resources/vantiva-and-vodafone-deploy-uk-markets-first-wi-fi-6e-gateway/

Yes, so still not Speedport.

Although I was mixing up Hub4/5 from Virgin Media, with Vodafone.

In a nutshell after speaking to both Vodafone and Sonos support, the older speakers don’t like the new WiFi 6 on the new routers. 

This thread confirms wiring the soundbar is a possible solution after speaking with support.

So ​@Mr. T currently has a better answer than the best answer in this thread, but the link to the thread with the best answer has no best answer. 

SonosNet is an option (ethernet-wiring the Arc to the Speedport); letting your Sonos products only connect to the Speedport’s 2.4 GHz WiFi is another one. Didn’t Sonos Support tell you this? So what are you more comfortable with?

​@craigski, My ISP provided me with a Technicolor router. I had to buy my own router to get my Sonos system up and running.

This isn’t the Best Answer either to the question asked.