When the Hp Officejet Pro 6978 not connected to wifi network, there are a few things that can be done to get it back on. The first thing that can be done is to make sure that the printer is not in sleep mode. The printer will go into sleep mode if it doesn't detect any activity for 10 minutes. To wake up the printer, press and hold the power button for five seconds. If this does not work, unplugging and plugging in the power cord will do the trick.