What version of Dreamweaver are you installing theme it into?
Do you have multiple versions of Dreamweaver installed?
If so, make sure you are looking in the correct Extension manager.
In Dreamweaver go to Commands -> Manage Extensions to open the extension manager for that version of Dreamweaver
If have seen a couple of cases where there was only one version of Dreamweaver installed and the extension manager was using a different profile if it was accessed from the application folder than if it was accessed from the commands menu, if this is the case for you, you will need to contact adobe support.