I’m not sure I understand. Are you running S1 or S2? Which Sonos speakers are showing up, but are not selectable? Have you rebooted your router? What device are you running your controller on? Which OS is it running? Have you called Sonos Support directly to discuss it? What did they suggest?

Thanks for your response.  Running S2.  Controller is iPhone app on current version of IOS.   The speakers are visible and selectable.  Once selected, I get the “Unable to Connect” message (with no suggestions for next steps other than “Try again later.”)
 

I conducted a router reboot.  No longer have the issue.  
 

Again, thanks.  

If this keeps happening or if you have issues after updates or power failures you may want to try assigning static/reserved IP addresses to your Sonos from your router’s DHCP Settings page.