Just a first basic check: is wifi turned on? 
Did you succeed in updating when they were plugged in? 
Have you allocated fixed ip addresses for your devices? (If not it’s worth doing so.)

Power of all devices and router. Restart router and wait for it to fully restart. When it has done, and wifi is running, restart speakers, one at a time, waiting for each to restart before moving to next. If this sorts the problem, the update/restart of the speakers may have resulted in duplicated ip addresses - setting fixed ones removed this problem. 

1: Wi-Fi is activated

2: Yes, they are installed correctly and updated while wired.

3: No, but I will try. Where can I find MAC-address for Wi-Fi-card on Play 1? If I am wired I guess I will se Ethernet MAC-address. 

@martinwesterstrand,

I would perhaps check and see that the router 2.4Ghz WiFi band is 802.11b/g/n backward compatible and check/set the security mode to ‘WPA2 Personal’. If the router also has QoS/Airtime Fairness features enabled, then switch those off too and then once again try adding the WiFi network credentials via ‘Update Networks’, as mentioned earlier.

Ok. Static IP gave me one solution and one new problem.

1: I got the both working fine on Wi-Fi with static IP. 

2: When adding them as surround speakers to my Playbase only one is connecting. Rebooting will make on or the other connect. Sometime its the left one, sometimes its the right one. Never both…

Thanks, but I have not made any changes in the router and it´s been working fine for years…

After a number of restarts I got both to connect and now it´s working as it should.

I’d be looking for potential wifi interference , particularly in the 5Ghz range, as that’s what the surrounds use to connect to your PLAYBASE. But it doesn’t have to be a Wi-Fi device, either, could be any electrical source. 

And now it’s not working again. 

As the Sonos Playbase is wired back to your router, maybe you have an intermittent hardware issue - perhaps grab two Sonos system diagnostic reports, one with the two surrounds connected and another shortly after they dropout and post the two reference numbers back here, then ask Sonos Support Staff to see if there are any issues with the Playbase or Surrounds 5Ghz adapters. You can contact/chat to Staff via this LINK.

I’ll check that. I thought play 1 only uses 2,4ghz. 
But it makes sense, I have really bad performance from my 5ghz network, both using my computer and my iPads. 
Have no clue what it could be though. 

I’ve had issues before…a new neighbor moved in, and was using the same channel I had on their new (and seemingly powerful) router. I’ve also had an issue where an older microwave was leaking RF interference…and obviously not a Wi-Fi device. That FAQ covers a lot of ‘common’ issues, but is not exhaustive. Shoot, even sunspots can cause interference that affects Wi-Fi. 

Today I got a new router from my ISP and a quick test shows flawless performance on 5GHz. 
Will now install Sonos to my new network using another SSID and password. 
I will post here later tonight(Sweden) how it works. 

I thought you had the playbase cabled to the network? Please note that the Play:1 surrounds do not use the routers 5Ghz WiFi network when they are ‘bonded’ as Home Theatre surrounds to the playbase. The two surrounds use a 5Ghz ‘ad-hoc’ wireless connection between themselves and the Playbases own 5Ghz wireless adapter, but their IP addresses are DHCP assigned by proxy via the Playbase.

If it was working okay previously with the old router, maybe a router firmware update has affected the DHCP address assignment via proxy (perhaps?), but I thought that you got it working for a while, so that seemed to rule out that issue.

Anyhow, that’s why I was suggesting earlier that you perhaps take two diagnostic reports, to try to discover what’s going on?

It might be the 5Ghz adapters on one of your devices is having an intermittent issue, especially as you did get the surrounds to work with your previous router. I’m not personally (yet) convinced it was a router issue, but maybe see how it goes. If the problems do continue with the new router, then I would maybe grab the diagnostic reports and go onto speak with Sonos Support. Anyhow I hope things get sorted for you.

@martinwesterstrand,
Usually if there is wireless interference between a Sonos Home Theatre product, like the Playbase and it’s surround speakers, the playbase will auto-select a different 5Ghz ad-hoc WiFi channel to use and certainly a reboot of the main player should sort the issue. The HT setup will even use DFS WiFi channels too these days and so that reduces the chances of them suffering wireless interference across the ad-hoc connection… a different router is, of course, a worthwhile troubleshooting step, but I’m thinking the answer to your issue here may still possibly lie elsewhere, but it does sound like it’s an intermittent matter, so it may prove a little difficult to pinpoint.

Keep a log. I once had a severe, intermittent issue. Some evenings were troublesome and Sunday was impossible. I slipped a copy of my log under my neighbors door, along with a polite note. A couple days later the log returned with annotations. She sometimes traveled for business and Sunday afternoon she called mom. She was using a cordless phone system known to cause severe WiFi interference on the 2.4GHz band. I was able to rearrange my connections and avoid her phone.

Update:

After installing new router the Wi-Fi connection and speed issues disappeared. Now I have a much more stable connection with average speed around 650Mbit. Probably Ken is correct that a Firmware update somehow changed the old 5GHz network, causing severe interference on all units using 5GHz. 

After four days of running the system I feel confident that the old router was the root to the problem. 

Thank you for your help. Made me figure out the issue and I learned a lot that I can use in my other home with more Sonos products. 

Have a nice summer!