Another Failure

You can try and see if rebooting everything helps. First unplug all your sonos devices. Restart your router/wifi. Wait for that to stabilize. Restart your phone. Plug the sonos devices back in. Wait a little bit and then start the sonos controller and see if they show up.

If that didn’t work, I would uninstall the controller app again. Reinstall, start and chose to join an existing system.

If it still doesn’t work, then the next best thing is going to be to contact sonos support and see if they can figure out what happened. Sonos Support

You really should contact Sonos and tell them that, this is a user to user forum with little Sonos participation..

Did you try the basic network refresh to recover your system after the failed update?

If not power down ALL Sonos devices, reboot the router and controller, wait for a couple minutes and power up the Sonos devices. 

If this gets your system working keep it in mind for similar situations after further updates, reboots or power fail/restore situations.

If it keeps happening you can try something some folks here will go to great lengths to assure you is unnecessary and never needs to be done. Still despite that it still helps some people. Use your router's DHCP Settings page to assign static/reserved IP addresses to all Sonos, then do the refresh above to make sure they are active.

Sorry you’ve had these experiences; many folk have not had update issues or concerns with their kit.
 

The pre-owned market for Sonos equipment is still strong, so I’m sure you’ll have no problem selling your speakers.