What device is the app running on? What version operating system? What exactly happens when you start it (a screenshot is worth a thousand words).

Thanks for reaching out.    I try with both my iPhone (iOS 14.1) and my MacBook Pro (high Sierra).   
 

sonos 2 (12.1.2)

router: (Askey/SAK2V1K)

It started this past Monday morning.  I could not connect to sonos.     Yesterday (Friday) I was able to connect to my Plabar that’s wired directly to my router).  It was wired fir a few days but not it’s up.   
 

however when I try to connect my two Play 3’s through the “+ add products” action, it just hangs on the screen I’ll attach here.   
 

one of my play 3’s is wired directly to my router
 

when I look at what devices are connected to my network (via My spectrum app) I can see my playbar and both play 3 connected.   It’s just not seeing it on sonos side.  
 

It seems like the issue is with sonos and spectrum (isp) communicating.   

Correction: my playbar (wired to my router) is connected.   It’s the other products (two play 3’s) that are not detected through either desktop or iPhone app.   

I was hoping this was as simple as the iOS Local Network entitlement, but given the random/changing nature of these issues it seems like whatever router you are using is majorly challenged. Can you get a replacement, or substitute a different model?

It seems the Playbar is wired, and that works, but the others are either SonosNet or WiFi, which does not work. I would start by hard-wiring everything, and make sure that works. Assuming it does, then one by one switch the desired-to-be-wireless devices to SonosNet (which I recommend over WiFi).

Thanks.   I’ll see what I can do about the router.  
 

I do have one of the play3 wired to the router but still not detected.  
 

mill look into sonosNet too.  Thanks again.