There's a couple of ways you can go about this.
Open a Command Prompt (Admin) and enter ipconfig /release followed by ipconfig /renew and then a reboot, but I would switch off the router and computers/devices, disconnect all cables for a couple of minutes, reconnect the cables then switch just the router on.
When all of its lights are on, switch just one device back on at a time.
This is known as performing a power cycle on the router which can resolve a number of connectivity issues.
BTW - What other device had you switched on to get that error message ?
