OK, I understand that you can scan with your HP Officejet J4550, and the image of the paper original that you have scanned, appears on the computer or is stored in a file there, successfully. And that your HP machine also prints out what is sent it from the printer.
But it won't copy. Blank sheets are the resultant.
I would like to ask: What buttons on the machine are you pressing to produce copies? do you press the START COPY BLACK, or the START COPY COLOR button(s) ?
Or are you using the HP Director software (or other HP software) on the computer, to signal to the printer that it is to do a copy?
As well as responding to the above questions, could you do a test print:
Press the Setup (little wrench) button on the HP machine's panel.
Then press > to select Print Report, press OK.
Then press > to select Self-Test Report, press OK.
It will print. It ought to look like this:
So: Does it come out like that (disregard the four brackets and their accompanying numbers, that's not part of the actual printout!), or not? is anything missing? if so what?
Does any of the printed textual information hint at a problem?
Let me know what you are doing, and what you find out, in reply, please. I am interested in this case.