Customers that purchase Book II from Basilisk Games
are given a registration number to unlock the full game. Digital Distributors in general use their own form of protection. As such, the serial number you were given from Stardock will not work with the Book II download from Basilisk Games.
Every digital distributor that sells Book II has been sent the latest version today.
Depending on how professional Stardock are and if any complications arise, they should update to the latest version in a couple of days.