Dear Mr. Boskovic,
I checked your licenses again and I found that the older AC 2011 license with the same serial number was not returned. Please, return the 2011 license before activating the 2012.
Explanation: According to th subscription, you received the new activation for the new version. This activation is generated for th same serial number, just with the different activation code. If the old license wasn´t returned, the new one can´t be returned.