Phantom Paper Jams in Canon PIXMA TR8520

Is this the bottom or top feeders? These are hybrid photo models. If the paper is jamming from the back, check for little scraps throwing the rear feed as it is a bit notorious if they jam up and stuff gets stuck. If you do not have any jam issues, inspect the rollers. They're probably fine on the back as it's meant for heavier papers 8/10 times (my TS702a has both) but it can still be more prone to ghost jams being a top feed arrangement. Sometimes things like dust can trip up the senors as well, so check for dust and get a can of canned air to blow it out if there's no visible paper scraps.

If the bottom feed is jammed, then you'll need to remove the bottom tray and then the jam cover. It's a lot easier to clear that if there's scraps, at least. Same thing - check for shreds and dust covering enough of the sensor.

As soon as this is done, power cycle the printer by unplugging it, and run another job. If the problem comes back, one of the sensors is bad.