Not sure what ‘all the suggestions’ really comprises, but if you’ve changed the network SSID that Sonos is to be connecting to, you need to tell it so. Since the network has changed, you no longer can connect to the speakers wirelessly, so you’d need to temporarily wire one of them, and wait until they all connect to the SonosNet signal. Some may require a gentle nudge by causing a power cycle. Once they’re all showing in the controller again, you can go in to network settings, and put in the corrected SSID and password, then remove the temporary Ethernet cable, and they should switch over.

Because you mentioned a separate building, which I’m hoping is merely a translation issue, all Sonos devices need to be on the same subnet in order to effectively communicate with each other. If your network is split into multiple subnets, just using the same SSID, the Sonos won’t be able to cross the split subnets, and ‘see’ each other, or the controller device. 

Sorry for not being perfectly clear. 

1. By separate building I mean a different network in a separate building where I already have a Sonos speaker connected (I’ve disconnected this speaker and replaced it with the one that I cannot connect to, and everything was fine, but when I return to the first building with a different network I cannot connect the speaker; the buildings are at completely different locations)
2. By ‘all suggestions” I mean everything suggested by the app and the (vanilla) help provided in the Sonos - including factory reset and following the instructions for connecting the speaker with an Ethernet cable to the router

Unfortunately, I cannot even get the sonos app to recognize the speaker when it is connected by wire (including following the instructions to restart the router and power off/on the speaker)

Unfortunately, I remain completely lost when it comes to finding a solution (although I still suspect some router compatibility issues even if everything worked before using the same router).

Would be grateful for further suggestions…

/HansH

Hi @hhatUven10 

Welcome to the Sonos Community!

The Sonos system requirements page may help, but I suppose the real question is: what settings on your router did you actually change?

If you don’t remember all the changes you made, it may be best to just reset the router.

I hope this helps.

Edit: if your 2.4 & 5 GHz bands are split (have different SSIDs/names), please make sure your phone is connected to the same band that you are trying to connect Sonos to. After setup, this should no longer matter.