I just recently bought the SoaSE bundle pack for the 20$... It now lists SoaSE and Entrenchment in the "My Games" list, but it says the SoaSE serial is invalid. 
The reason this has occured might be because I had been using my fathers account on this machine beforehand with SoaSE installed... could this be the issue?
Any other help would be appreciated 
Edit: I can supply my order number/serial number if required as well.
Edit2: Problem fixed, searched around the forum. Dash provided a link to a registry fix to another member, and it worked for me as well. 