Have you recently made changes to your network (network name, password, router, internet service provider)? If so, you can re-do the wireless setup from the operation panel of the printer itself.
Press the Menu button and go to WLAN setup, press ok. If it asks you to press and hold a WPS button, press the STOP button on the printer, then you should see an option for Standard Setup. Press ok and it will look for the networks near you. Select your network, press OK and then enter in the password. Should get you up and running again.
