If you're working at the 2nd floor desk and you find that the printer is saying that it's jamming A LOT, but you're not finding paper jammed in the machine, check the green guides in all the trays, especially Tray 1. The green guides hold the paper snugly and should be lined up with the mark for "8 1/2". If it's off the mark, the printer will be unable to pick up a page with its rollers.
If you are re-filling paper, that would be an excellent time to make sure that these guides are aligned correctly.
See photos for comparison: