Beam Gen2 surround fails with Era 100's on wifi.

Not sure what Reddit was talking about, there has been no corrupted firmware update I’m aware of. 

Factory resetting isn’t terribly helpful, either, at best it erases any data stored on the devices that might tell Sonos what is going on. It certainly rarely, if ever, helps a situation.

The surrounds for a Sonos system connect to the main soundbar ( your Beam in this case) to get surround data. When you transfer them from ‘regular’ speakers to bond them as surrounds, the switch from a direct connection to your router to a direct connection to the soundbar. This ultimately means the WiFi/radio must be turned on on both the surrounds, and the soundbar, even if the soundbar is connected via Ethernet cable. There’s a secondary setup that allows you to wire both the surrounds and the soundbar to the router with cable, so you can turn off the WiFi/radio portion in the software, but I don’t recommend it. 

While I have an Arc and Era 100s as surrounds, they’re working perfectly. Given that the software and firmware should be the same, yours should be working too.

If you’re having an issue, I would certainly recommend that you submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it. Don’t post the resulting diagnostic number here, Sonos’ lawyers get sensitive about GDPR, I suspect.

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.

There is an official Sonos presence on reddit that is usually trustworthy but in my experience there is far too much bad information from other sources there. Here isn't perfect but the really bad stuff is usually called out.

As said there was no corrupted software update but sometimes Sonos does get confused by an update or power failure. The first step of the cure is to not make things worse with a factory reset.

Instead power down all Sonos, reboot router and controller, wait for it to stabilize and power up the Sonos. Main speakers first, then Sub and surrounds.

From where you are now, and as the post above suggests you would be well served to remove the Ethernet and enable the internal radio (reenable the wifi) essential to the surround connection working properly. Do the power cycle as suggested and things should return to normal. 

Thank you Airgetlam and  Stanley_4 for your replies.  With a renewed effort I finally got connected and have my system working fully on WiFi although it was a struggle and I don’t know definitively what was wrong in the first place.

I  created a 2nd network on my router dedicated to my Sonos system on the 2.4GHz band.  New attempts to connect the Era’s to the new network failed.  Beam went smoothly.

In the end I did have to factory reset the Era’s and reinstall the app on my phone because even after deleting the old network from the app the Era’s would still connect to the old network.

Happy to know that the firmware was not the problem.

I also note better performance as occasional pulsing noise from the surrounds (mostly during sporting events) is gone.

This is a steep learning curve so I’m glad that people take the time to offer advice.

Kind regards...