Hi, All HP inkjets has mechanical-optical sensors. One for head carriage clear strip w' faint lines on it is just behind the printhead carriage. One for start of paper just before the printing area. Finally on HP printers that moves it's head to reach for cartridge when top cover is opened has one mechanically linked to the swing-up cover. The problem lies in that start of paper sensor. I think dust bunnies blinding that sensor or that long black flexible wand w/ hole in paddle end may had got jammed or jumped out of optical switch gap. You can see it without opening printer up with flashlight. That horizontal black wand pointing towards rear pivoting in the stainless steel paper guide is gravity operated. Paddle (wand) side should fall down when paper slides past that wobby part when paper is not on that sensor, the wand end is up. Wobbly with wand part looks like small ribbed black block with wand sticking out back thing sitting in the hole for stainless steel paper guide just behind and under that printhead carridge. Did it make scary loud Griiiiiiiiding noise every time you turn it on and LED lights alterately flashing? That fatal condition and bit of work to fix. It's the "shifter" vertical stick behind that park/cleaning station that set the height of sealing pad at each turn-on. Small stop nub on that plastic lever breaks off and sealing pad assembly keep going up and up then GRIND noise you hear. Then printer stops and alterately sets of LED flashing. Watch the printer parking/cleaning station at each turn on every time head moves aside to clear that station, a motor raises that thing and it stops at certain with short mild "Grrr!" then micro knows the "set" height of that station due to that vertical stick. When done, the head moves back over that station, head carridge pushes aside that stick and lets the station to rise and it's at correct height as long as power is on. Cheers, Wizard