I believe he's talking about printing in the flight planner, which is different than the knee-board and you are able to print from there.
First question, do you have the latest drivers installed for the printer? Can you print from other programs?
Next question: After you click print in FS does it come up and give you a print properties dialog box?
Usually after you click print it will come up and ask how many pages, etc before it will print. perhaps it tries to pop up in the background? try running FS in a window if we are in full-screen now and see if you get a print dialog box.
I don't know what to tell you yet...
