I don't have a 520 in front of me, but I am assuming you mean Printer Menu is set to "yes" meaning "On". If the batteries get low, it automatically turns the printer off and it would manually need to be turned on, regardless of anything else you do.
If the menu says "On" than I would think it is one of two things. First I would check the paper roll. Sometimes these are not seeded properly, and only halfway seated in its guides. This would keep the printer and paper feed from working. If the paper roll is in its guides properly, and the paper is already in the paper feed, and you can pull it easily, it probably isn't this. I would then check the connector inside and see if it has come loose, I would open it up and check that. If all looks good there too, call your Tag Heuer distributor. If you are in the U.S. that is Reliable Racing, but good luck getting someone on the weekend....make sure you ask for a loaner before sending yours back as repairs usually occur in Switzerland and take MONTHS.
Jenna