Found your reply and experiment very interesting but it has brought me to the conclusion that your model of printer, and mine, are both not actually fit for the purpose of printing photos, which is the reason I, at least, bought mine.The Troubleshooting advice they give does not sort the printing problem. It is also annoying that my 5520 won't switch back on after being turned off, unless I remove the plug and then plug it back in to the electical socket. Seems it was a bad buy all round and I am not prepared to keep taking my printer back over and over again until I do get one that works. I don't have that kind of patience, or petrol money!
(It's a bummer that you are stuck with keep trying different printers solely from Staples though if they will not do a refund to your card to enable you to go elsewhere - I would be very cross about that if it seems they have a bad batch of printers in stock. Maybe you could point that thought out to them and see if they will relent and give you a proper refund? Good luck anyway.)
I'm off to research other makes of photo printers now but will keep an eye on this thread in case anyone can come up with a definite solution before I take my printer back to Argos!