We have noticed this topic gaining some traction of late. If you are having issues with the above, please check the following. 

• Ensure that you are in one of the Support Regions for Alexa on Sonos. 
• If you are, next try the advice in this post: 

  I had the same issue. Here's how I managed to re-add the speakers.
  First, I changed the names of all my speakers from say "kitchen" to "my kitchen".
  Then I disabled the skill, re-enabled and started a new device discovery. Nothing.
  Then I changed the names back, and suddenly they were discovered upon rescan

• If still not able to resolve this problem, please check this thread: Resolving the majority of issues with Alexa on Sonos. 
  
  If you are still having issues after trying all of the above, please feel free to start a new topic, or respond below with a diagnostic confirmation number and we will look into this for you at our first opportunity.