To adjust the keyboard backlight on your HP ProBook 4440s, you typically use the "Fn" (function) key in combination with one of the function keys that has a symbol representing the keyboard backlight.
This is why doing Firmware Upgrades is so risky. The firmware tells the printer what to do when it switches on before self testing and loading software. If the Firmware is corrupt, the printer becomes a giant paperweight. Help here
Question edited for clarity and toss in some CAPS.
Open all the doors including the bypass door and remove the trays. Get a flashlight and look for a tiny piece of paper covering a sensor. Also try this for a false paper jam error state. Check the Auto document Feeder (ADF) as well, last video.
Reset the printer, which might clear a false paper jam error, and then try to print again.
With the printer turned on, disconnect the power cord from the printer.
Unplug the power cord from the power source.
Wait 60 seconds.
Reconnect the power cord to a wall outlet and to the printer. note: