In my case, this error was when trying to connect to new WiFi (new router) was incorrect.
Uninstall the Sonos app, reinstall and factory reset your Sonos and it will then connect - there is a bug in the Sonos app. The uninstall and reinstall will also trigger an update to the Sonos One SL and the device will then connect.
Hey
Thank you for providing this workaround.
Indeed is the ability to change the network via the Sonos App not available with all speakers and is being worked on to be available across the entire Sonos ecosystem again.
In the meantime another option to change the router for your Sonos system, if possible, is wiring one speaker temporarily as described here: Switch Sonos between a wireless and wired setup
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