That's not what it said. What it said is that you have two PS3s activated under your PSN account already, so you can't activate this PS3 in order to download anything from the Playstation Store; including this map pack. It has nothing to do with Black Ops 2 DLC specifically. Apparently you have been downloading your Playstation Store purchases to other people's PS3s, which is not allowed. Follow the instructions on the link below to deactivate those other consoles.