Hi Ella,
I'm not THE specialist in this domaine, but, there is a transparent thread inside printers you have to clean from time to time for it to work properly. With mine a HP 7300 all in one, I was about to buy another printer but called HP first. They guided me through it and since, every time I have a problem with a printer (my sister's or friends') I start by cleaning that thread. It's inside, next to the line directing the ink. Be carefull, It's very thin, you just pass a wet tissue on it and do the operation until no ink smears the tissue.
The thread might not be very 'transparent' if you never did it before. Honest, mine was black with ink and the HP-man was close to rude because I couldn't find a Transparent thread but trust me it's there.
Hope this helps, if no one comes up with a better idea or the real solution.
Good luck
Zara