Best answer by jgatie
Reboot/power cycle your devices in the following order:
Modem
Router
Switches or hubs
Wired Sonos units
Wireless Sonos units
Computers/printers
Wireless devices - phones/tablets etc.
Allow each device to come back up before proceeding to the next. Note that you can permanently prevent duplicate IP addresses by assigning an IP to each device's MAC address in the router setup. See your router manual for details.