It’s not clear in your post as to whether or not the speakers were unplugged when you rebooted the router, or how the speakers normally connect, or what kind of network you have. 
 

At the least, plug an Ethernet cable temporarily in to one of your Sonos speakers. Then unplug the speakers from power. Reboot your router. Plug the speakers back in. Wait 5 minutes before opening the controller. Test. If everything is showing up, great, check the ‘network’ settings in the controller and then  remove the temporary Ethernet cable.

If it’s not all working, call Sonos Support directly to discuss it.

Thanks for the reply…. Finally talked to Sonos Support and learned that all were dead. 3 Play 3’s and a  Beam. Didn’t try your fix and will do that before I send them back. THANKS

Same here. Our 2 Play 3s were working fine a couple of weeks ago and they’re both dead, no light comes on. They were plugged in to different circuits, we have not had a power outage, they haven’t been moved, etc. Did the “fix” mentioned help you? 

Do you have any other devices in your Sonos system? Do the Play:3s show up in the app?

If the two speakers are really dead then a power surge cannot be ruled our.  This does not necessarily require an outage and could affect products in different sockets.  Do you have surge protection?