Sonos One - Cannot Connect

Please allow me to talk through this, just to get my thoughts in line.

Your system is using SonosNet, as you have your Beam connected to your router via a cable. Your surrounds should be connecting to the Beam as normal on the ‘hidden’ connection, which is a 5Ghz channel (very low latency, not much range). 

There is no ‘difference’ between US and any other countries’ speakers, other than the plug for power, so that isn’t a concern.

You state you’ve rebooted the One, which would certainly be a step I would normally take as well. But, I’d go a step further, and reboot the device that is generating the SonosNet network, too, I.e. the Beam. Then see if the One can recognize the SonosNet network and connect. 

If that doesn’t work (and I think it should), I’d be tempted to do a factory reset on only the One that won’t connect, and not on any other speaker in your system. Then try setting up that speaker as a completely new speaker. I’d be tempted to remove some variables by also temporarily wiring it to your router, and keeping the Beam wired, once it is connected to your system via the ‘add a device’ function in the controller, you can remove the Ethernet cable, unplug it, and move it to where you want it to ‘live’.