Batman arkham city serial?

i have BAC on disc for pc

i hace installed it and it asks for a serial number to activate the game so i can play it

i have tried the authentication code in the game manual but claims it is invalid

i can not find any other code anywhere in the box on the disc etc

please helpBatman arkham city serial?
The serial shud be at the back of the disc... If not try searching in the disc..Batman arkham city serial?
If it's invalid and you bought it new then you need to contact the publisher or exchange it for an identical copy wherever you got it. If you bought it used then there's not much you can do.