Not your problem.

It's new Sonos app which is faulty.

Or you retry until you are lucky.

Or we wait a new hopeful release 

Could be your home wifi ‘Network Name’ ? I read you did factory reset the devices and are able to add. Just wondering if you changed your new home Network Name to match your previous home network name that your Sonos devices were previously on, perhaps the devices will recognize and appear in the app. Maybe, Worth a try?

also, after attempting the above. Try to ‘Reset App’ (Home->App Preferences->Reset App) It will prompt you to force close the app and then you have to relaunch it and sign-in to Sonos again.

There was no need to factory reset your system, Sonos already has a new router - installation instructions FAQ. You may find it helpful to temporarily wire your Arc with an Ethernet cable, but I’d likely call Sonos Support directly to discuss it.

I have same problem. Trying to set up at new home and wouldn’t recognize. So I completely reset all products and they were able to join etc.  I even went through the true play exercise. It all works when I play through tv but nothing will show up on the app now.