HP Officejet Pro 8620 says the ADF is jammed. We have followed all the steps in the owners manual and the online tutorials, including unplugging the power from the back of the printer and unplugging the power cord from the power source, and plugging back in. We still get the screen " The original is jammed in the automatic document feeder (ADF). Open the ADF cover, remove and reload the original, and then try again." No success!