I have an S415 all-in-one that has been very easy to use. Suddenly however, the printer receives a job from the computer, sounds and behaves as if it were printing, but nothing is actually printed on the page. So I removed the (generic) ink cartridges that were there, and installed brand new Lexmark cartridges. When I then sent a pdf to the printer, once again, pages were blank, except for the yellow highlighting I had done on the pdf. So, I suppose that means the black cartridge is a problem. So I removed that cartridge, put it back in... and still no black ink. Any ideas?