Sonos tends not to play well with devices like Powerline extenders, that’s not terribly surprising. However, there are a couple of things to look at for the WiFi issue.

First, while it is connected to your router with that cable, and showing up in the controller, make sure that in the room settings for the PLAY:3 that the WiFi/radio hasn’t been turned off. I’m not near my system to check exactly where that is in the menu structure, but it’s buried in the room settings.

Unfortunately, it may still be ‘on’, so try toggling it off, then on again, and do a quick test. But it’s also possible that the WiFi card in the speaker has failed, so I would recommend that you submit a system diagnostic while it is connected with the cable to the router, and call Sonos Support to discuss it, or post the diagnostic number here for a Community Moderator to pick up.

There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.

When you speak directly to the phone folks, there are more options available beyond just the diagnostic analysis.