Diagnosis
The protective shipping tape inside the toner cartridge compartment wasn't fully removed, blocking the toner from reaching the imaging drum.
How to Fix It
Power off the printer and open the front door. Pull out the black toner cartridge (the only one you install). Inspect it closely—you must remove TWO clear plastic tapes: one along the top edge and one wrapped around the cartridge's side/seal. Remove any remnants, reinsert firmly until it clicks, and close the door.
If That Didn't Work
The transfer roller (which moves paper through) might be contaminated. Power off, open the rear door, and look for a wide, gray roller. Gently wipe it with a lint-free cloth dampened with distilled water, then let it dry completely for 10 minutes.
Heads Up
Never use isopropyl alcohol or standard cleaners on internal rollers; it degrades the rubber and makes the problem permanent.