Physical Dragon Age 2 has incorrect Activation Key

I recently bought a physical copy of Dragon Age 2, and am having problems activating it as the activation key on the back of he instruction manual seems to be incorrect. The installation process asks for a key with 20 characters (5 groups of 4), however my copy of DA2 only has a 16 character ey (4 groups of 4). The installation doesnot accept the short activation key, and when I try to redeem it through Origin, it is recognised as a key for the Black Emporium bonus content (which is also included in the game box on a separate slip, so I am definitely not confusing the two codes).

How can I resolve this and obtain a working (legitimate) key? Thank you in advance.

EDIT: Just realised that there are posts to the forum already of plenty of people having this same problem. In that case, any tips as to the best method to resolve this issue quickly?