Best answer by Airgetlam
Then, try plugging an ethernet cable between the PLAYBAR and router, and see if it shows up then. If it only shows up when connected with an ethernet cable connected, I'd run a diagnostic of your system, and call in to Sonos and discuss it directly.
But I suspect that a simple reboot of the PLAYBAR will likely "fix" it. Might be worth rebooting your router while the PLAYBAR is unplugged as well, and let the router come back up before plugging in the power to the PLAYBAR.
But at the end of the day, there's a computer inside every Sonos speaker. A small one, to be sure, but it is sensitive to all the things that your regular computer is, specifically power surges, so they can fail. But it's pretty rare for that to happen.