Remove, and then insert the imaging unit.
Warning—Potential Damage: Do not expose the imaging unit to direct light for more than 10 minutes. Extended exposure to light may cause print quality problems.
Warning—Potential Damage: Do not touch the photoconductor drum under the imaging unit. Doing so may affect the quality of future print jobs.
Print the document.
Does gray or colored background appear on prints?
Contact customer support.
The problem is solved.