DIAGNOSIS The paper pickup roller inside the printer is either dirty, dusty, or has worn smooth, so it can't grip the top sheet in the tray. This happens a lot with this model if you use it infrequently.
FIX Turn the printer off and unplug it. Open the rear access door (the one where paper comes out). Look inside and to the left—you'll see a gray rubber roller. Dampen a lint-free cloth with a little distilled water (not isopropyl alcohol on the rubber). Manually rotate the roller with your finger, wiping the entire circumference clean. Let it dry for a minute, close up, plug in, and try with a fresh stack of plain paper, making sure the guides are snug.
IF THAT DIDN'T WORK The paper sensor, a little plastic flag inside the tray area, might be stuck. With the printer off, remove all paper. Use a flashlight to look in the empty tray slot. Gently wiggle any small plastic lever you see with a pencil eraser to free it up.
HEADS UP Overfilling the tray beyond the 100-sheet mark puts pressure on the mechanism and makes this failure happen faster. Also, glossy or heavy paper is harder for this entry-level roller to grab consistently.