I had the same issue with my C4780. I didn't hit any button. I just used the HP setup utility , and chose WiFi. It was trying to transfer wireless settings, and the printer magicaly disconnected. The HP support had me reset the printer, to no aval. After the reset, it wouldn't move past the HP screen. The decided to credit me $139.00 even though I got the C4780 with a Mac for $30. I bought a different HP All in one. It should come Saturday. The rep said the C4780 is known for WiFi issues, and the WiFi bricking the printer. Needless to say I can keep the defective C4780 and my new printer. So I took the C4780 apart, and removed the WiFi card. It now works. just no wireless. 🙁