Always use a new cleaning pen on the printhead. (An old pen carries contaminants from its previous uses that may damage the printhead.)
The printhead becomes hot while printing. To protect from damaging the printhead and risk of personal injury, avoid touching the printhead. Use only the cleaning pen to perform maintenance.
When you load new media, you can also clean the printhead.
Rub the cleaning pen across the dark area of the printhead. Clean from the middle to the outside. This will move adhesive transferred from the edges of the media to the printhead outside of the media path.