There is an analogue switch, probably in teh rear of the paper tray slot, that is wither defective or blocked somehow. Pull out the paper tray and get a flashlight and look at the back of the slot and see if you dont have a small piece of paper jammed in there somehow. As Eric has already suggested, make sure all fo the panel doors are secure. That seems somewhat unlikely as HP's will generaly give you a door open error message. But then, it is an HP after all!!!
Noli Nothis Permittere Te Terere!!
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