why wont it use the full ink cartridge when 1 is empty

[scorpionqueen]

I have a HP Photosmart 7520 Printer.  It holds 3 color cartridges and 2 black cartridges.   One of the black ink cartridges has a bow tie symbol on it the other a pentagon or hexagon. Those symbols aren't on the outside of the box though.  you don't see it until you unwrap the ink cartridge and use it.  Why if the black ink with the bow tie is empty, but the other one is new and full, will it not switch to the full one?   Also I always buy all HP ink products from Wal Mart, but now a message comes up that one of my cartridges is counterfeit or not genuine HP.  Why would it do that?.

[Valsimot]

The printer model uses 2 black one normal and the other is photo black they are different. And that is the reason symbols are different and the outer box is different.

The hexagon is normal black, and the bow tie is photo black, the both 

The printer can't switch from one black to other, you need to have all cartridges installed and full to be able to print.