Slitherine

I am getting an "Invalid Serial Number" alert when trying to install Grand Campaign 39 (also for '40).

Originally had digital download of game plus 39-43 Grand campaigns installed on another home PC. That machine is being retired so loaded game CD and patch on new PC. Both loaded OK but campaigns will not.
Ideas?
thanks!

You must be using the wrong serial number. Each DLC, and Panzer Corps as well, have different serial numbers.

D'oh! Kept trying to use the serial no. for the base game instead of unique for that campaign.
thanks!