Without much detail in your post, it’s hard to be definite, but one of the more common issues is the network that the Sonos relies on, and the potential for many routers to hand out duplicate IP addresses. 
 

Before submitting a diagnostic and contacting Sonos support directly, I’d recommend a simple refresh of your network. Unplug all Sonos devices from power. While they’re unplugged, reboot your router, and give it a couple of minutes to come back up before plugging your Sonos devices back in to power. 

I appreciate that these things are hard to diagnose. We’ve had Sonos for quite a few years now. I’ve done exactly what you say, which takes some time, and it sometimes works for a day, and then the next day, doesn’t work! I’ve had multiple routers, doesn’t matter. We have Comcast internet. We have iphones, streaming TV, a printer...all of which always work on our Wifi. Only Sonos consistently or inconsistently fails to connect. If it was a consistent fix, we would surely do it. But rebooting everything every night so you can listen to music defeats any advantage of the system. Are we missing something obvious? 

Describe the network. Is there a mesh WiFi system? How does the Sonos connect to the network? How are the iPhones configured in terms of their network connection?

I’m truly sorry you’re having such difficulty. It is unfortunate that Sonos relies on a good network to work well, but without that, you’re going to continue to have difficulty, especially as Sonos uses your LAN in a substantially different way than all the other devices you’ve listed. They’re all mostly ‘device to internet’, whereas Sonos is substantially ‘device to device’ within your LAN to maintain the ability to play in sync, as well as then needing to access the outside internet. 

I would suggest that if you’ve already done what I suggest after a Sonos software update, which is when this router error most frequently is exposed, then you should submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it.

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 phone folks, they have tools at their disposal that will allow them to give you advice specific to your Sonos system and network.

I’m not an IT expert, but generally have no other trouble with technology. The wifi is standard, as far as I know. I don’t think it’s “mesh” just because I don’t know it to be. Sonos connects to the wifi network the same way everything else does, as far as I can tell, just that it does it one day and not another. It just shows up working, or not. Gosh, if this was obvious to me or easy, I wouldn’t be here. I’m even hesitant to post about it because we are so fed up. It now seems easier to connect our damn phones to a bluetooth speaker or cable connection and play spotify that way. 

As Bruce has said, a system like Sonos places more demands on a local network than something which simply needs to talk to the internet. 

You'd better deal with Sonos Support. 

That sounds much like issues I had here. I have no idea why the fix works even after many hours of reading network logs and probe data. But it did work.

Go to your router’s DHCP page, assign a static/reserved IP v4 address to each Sonos device.

Power down all Sonos.

Reboot router and controllers.

Power up a wired Sonos device if present, otherwise do the closest to your router Sonos.

Give it time to boot up and stabilize, power up the rest of your Sonos one at a time.

That fixed my random problems, won’t update and restart problems, won’t come back from a power interruption problems.

This isn’t a universal band-aid, but it only takes a few minutes to update the router and one power/reboot to see if it will work for you.

@Salish,

In addition to reserving the speakers IP address in the routers DHCP reservation table, as suggested by @Stanley_4 , I would also certainly opt to fix the routers WiFi channels, as many routers often change channel on update/reboot/startup. I would certainly fix the 2.4Ghz WiFi band to use a non-overlapping channel, either ch1, 6 or 11.

@Salish

Judging from your last post of 15 hours ago (time at this writing) you may never see this comment but I‘ll post it anyway. Your original post seems to indicate that you’ve enjoyed your Sonos relatively issue free until recently. You also stated that Comcast as your ISP.

Question/Statemet: Are you using another router in addition to the Comcast box? If so you may be broadcasting two wi-fi networks. Since the Comcast box is most likely a combined router/modem its router section should be placed in “bridge mode”. Granted I’m only grasping at straws since you didn’t provide any information about your network configuration.

Hi Folks,

I got in and did reserve DHCP channels for Sonos and after having to go through the whole set up process again on the Sonos app, I got them to work! Now, the question will be whether it works the next day. I’ve had these speakers for quite a few years, and it has had this problem on and off for most of them. We’ve just lived with Sonos being a total pain in the butt. We love the concept, and sound quality, but this connectivity issue has meant that fully half the time or more we can’t listen to music when we want. So thank you for the technical guidance and I will try the other things suggested by ken griffiths. 

I got home and Sonos wouldn’t work, as usual, despite me getting it to work last night. I did what you suggested and designated the 2.4Ghz band to channel 6, and suddenly it’s working and available to Spotify and the Sonos app. Thank you! Absurd that an over the counter mainstream product would require this level of technical digging to get it to work, but there you go!