HP officejet J 4680 not printing

Hi hope someone can cure this annoying problem with my printer.This printer was working fine till yesterday but now will not print anything i send it, display says printing, paper goes in but comes out blank.I have tried re aligning cartridges and it prints the test page okay, so does anyone have a clue what is going on.

I'm sure this isn't the case, but I remember helping a friend of mine a few years ago with a similar problem.

Eventually found he'd set the font to white so the printer was printing white text on white paper.

Ho hum!