so the printer is connected to the router by cable or usb or wifi ? I think you can directly connect the printer to the computer to test

did you try multible devices? If you tried but same error , I kind think it's the 802 itself

I think you need to send your issue directly to the support for further troubleshooting now.

the Norton Core router broadcasts a wifi signal and your phone can connect to it and access internet on the wifi, correct? if so, you may follow this FAQ to set up the extender:...

The RE305 works at Proxy mode by default, so you need follow the steps of the Proxy mode part in that FAQ

Are you using the default wifi password printed on the bottom label of the WR802N? if it doesn't work, you may try a factory reset: with it powered on, press and hold the reset for about 10s until it...