There are 2 power buttons as per the manual.
a Single Square button in the middle of the printer which is the primary power source(I/0) where I is ON and 0 is off , and a secondary circular red button at the top of the back panel which is for the printer (which is a push button on/off switch)
Both should be ON
Make Sure the -
-the USB cable is connected
-Refresh printers and faxes and the printer should read online