It says there's a paper jam or a scanner misfeed..but there's nothing there

Paper stuck inside the HP All-in-One can cause jams or also sometimes there are some instruction that get stuck in the printer internal mechanism .
Power off the printer , unplug the power cable. Wait for 30 sec. , Replug the power cable. Power on the printer.
Check for a stuck paper or torn bits of paper.
Clear jam from the back of all-in-one
Press in the tab on the left side of the rear door to release the door. Remove the door by pulling it away from the HP All-in-One.Trying to clear a paper jam from the front of the HP All-in-One can damage the print mechanism. Always access and clear paper jams through the rear door.
Gently pull the paper out of the rollers.If the paper tears when you are removing it from the rollers, check the rollers and wheels for torn pieces of paper that might be remaining inside the device. If you do not remove all the pieces of paper from the HP All-in-One, more paper jams are likely to occur.
Replace the rear door. Gently push the door forward until it snaps into place.
Press OK to continue the current job.
Clear the jam from the automatic document feeder (ADF)
Paper can also jam in the automatic document feeder. Follow the steps below to clear a paper jam in the automatic document feeder(ADF)
Lift the cover of the automatic document feeder.
Gently pull the paper out of the rollers.
Reload and test the all-in-one
Once you have removed the jammed paper, verify that the all-in-one is still functioning properly.
Reload the all-in-one with either plain or photo paper.
Print a page from a memory card or the computer.
If you have completed all the steps listed above and are still experiencing a problem contact HP to service the product.