So I purchased an ES44AC, got it today, tried to install it in 2004, 2006, and 2009 but it keeps telling me serial number not found and I have the latest version of gatekeeper because last month I purchased a C44-9W from the site and everything was okay because I got the same error, shut the computer down and it worked. This time, not so lucky, and I tried to install gate keeper, but it said installation destination not valid. Can someone help me? Thank you.