I don’t believe that “the app managed to delete the sound system” though no doubt something is wrong. 

Did you add the new Beam to your existing system, or did you create a new system?
 

Try powering off the Beam, restarting your router and existing system and phone, and see if that reconnects you to your system. if that’s ok, factory reset the Beam, connect it temporarily to your router with an Ethernet cable, and then try adding it to your system. 

Thanks for your message. 
 

I'm pretty sure i tried to set it up in existing system. 
 

i did as per your steps, but the app cant find the system on the Wi-Fi. 

What should I do?
 

 Can you see the Sonos devices from within your router settings?  Can you access your router from an app?  If so can you see if the Sonos devices are seen by your network?

Hi,

Yes, pls see screenshots. Can see them in the router app as well as on airplay and can play music on them. Any suggestions? Believe it is very strange.

Before they came up under devices on Spotify. Not anymore. Now I need to go on airplay.

 Does your router broadcast a 2.4GHz & 5GHz SSID?  If so do both SSIDs have the same SSID name & same password?  Does your phone have a VPN?

Yes, same name and password. I have VPN installed, but not active. 
Don't know what to do…

Hi everyone,

The app can now find some of the speakers in my system. I think it might be a Wi-Fi problem. Want to ask you.

My setup is that the fiber provider gave us a modem and router combined. I have a switch between that and the various ethernet output in our house. I have bought mesh routers and plugged them into ethernet. I have disabled the Wi-Fi on the modem / router provided by the fiber provider and using the Wi-Fi from the mesh routers I have bought. Might this be the reason the is difficult? I keep on trying to set up the new beam with factory reset and it does set up until it tries to connect to the Wi-Fi from the mesh router and then nothings happens until a message says that the beam is set up but might not show in the system and that I have to unplug and set it up system settings but it does not show after unplugging.

Thanks for your reply. 

 is the Beam connected to a node via Ethernet?

 When Sonos says  “… finish setup from the System tab.” It sounds like they mean setup from the PC app.  Where would a “tab” be in the 80.x app.

 What brand is your mesh?

No, tried to connect the ethernet to the beam, but when the beam was supposed to make a sound so that the app found it it didn't make a sound. But when trying to set up by Wi-Fi it makes the sound…

It says system settings, not tab. So how I understand it is under system settings in the app and the speaker is supposed to show.

Mesh is Deco XE75 

 Sounds like you do broadcast both 2.4GHz & 5GHz so I would think the Beam should connect.  The Beam does need to connect to 2.4.

 Some have suggested disabling Guest Network in the Deco.  Also disable the 5GHz network during setup.  Then re enable the 5GHz network once connected.

 There are folks in this community with way more experience with mesh than I.  Hopefully they will give you some ideas if the above doesn’t work.