With Backup Exec, only the licenses that had current and properly linked support contracts at the release of version 12, 18-FEB-2008, can be upgraded.
Activation keys can be for more than 1 licenses, you would not necessarily have 19 keys.
If you had a support contract on all 19 BE11D AWS agent licenses, they were/are current at the release of 12, and you have not had any gaps in your support coverage, then you should be able to upgrade them to version 12 based on those assumptions
I have spoken with many customers, and the most common reasons they did not receive their version upgrade notifications was: Their spam filter caught the upgrade notification, there is no email listed, or and incorrect email {misspell or no longer valid} address is listed
If you believe you should be able to upgrade all your Backup Exec licenses, but did not receive upgrade keys, contact your regional customer care department: http://www.symantec.com/business/support/assistance_care.jsp