Your system not found on [wifi]

Factory resets are so disruptive, erasing all data previously stored on the system, such as account, streaming sources, playlists, and even error logs that Sonos could have read to possibly help you. 

One thing it rarely does, which reading your post seems like the most likely issue, is reset the IP addresses being held in your router for the Sonos devices. Try a network refresh, by unplugging or powering down all Sonos devices, then reboot your router. Wait two minutes for your router to reload its firmware, and settle in, then power back up / plug in your Sonos. 

If this doesn’t change your issue, I would recommend that you submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it. But 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.

Yeah, that’s not the answer. First of all, this was a clean setup, the router had never seen the devices. And I had done plenty of resetting before. While the router might re-assign the same ip-address if to the same Sonos device if you factory reset it as it did before, there is no reason why it wouldn’t do that after you reboot the entire network. If Sonos doesn’t work if a particular device ends up with a particular ip address it would mean that the Sonos protocol is rather broken, no? Every time the DHCP lease expires it would be up to the router to re-assign the ip address.

Factory resets are mostly fine these days. You need to log-in again, sure and reconnect your sources, but I keep my playlists at spotify.

The issue got resolved after adding more elements to the system doing more factory resets. Possibly that made the Sonos mesh network better. 

Something is broken with Sonos and IP addressing, some folks have no issues, some every reboot is likely to fail, others are mostly good but every once in a while things go wrong.

I have spent many hours trying to find out exactly what is going wrong with no luck.

Setting static/reserved IP addresses does seem to avoid the IP address issue. 

I am to the point I use the speaker’s MAC address on the Sonos shipping label to assign addresses before I even unpack any new Sonos I buy. Works for me and no reboots needed.