I know Sonos can be picky at times with wifi. Tried reconfiguring the wifi on the Sonos? The recent changes to the firmware's wifi may perhaps require a client reconfiguration.
Sonos Support
support.sonos.com
Thanks I did try to do that on rc7. They all were able to connect on wifi, however, they all were not able to group together. I will try it again though and provide feedback. Thanks