1.Turn off the printer or all-in-one, and unplug it.
2.Wait 30 seconds.Plug the printer back in and power it on.
3.A changed security setting (SSID,Encryption, ) on your router
4.Reconnect the ethernet cable to the router and printer network port, or
Try a different network cable, or
Hook up and test a different network-ready device, or
Connect the cable to a different port on the router.
I hope this may help you.. thanks