Design Extender - Site Import

I am using Dreamweaver CS5.5. Quite a while ago I was using Design Extender with my older version of Dreamweaver. I then upgraded to CS5.5 and no longer used it. Several months ago I needed the Site Importer, I went to your site and downloaded just Site Importer (WA_SiteImport304) and installed it. I just tried to use it again (after quite a while) and when I clicked on it, nothing happened. So I went back to your site and looked at my downloads and now only see the Design Extender, so I downloaded that. When I try to install that, I seem to be doing something wrong. First, I saw the Site Importer in the Extension Manager and your instructions say to uninstall any other versions of that, so I did. Then I click "Install", browse to the downloaded file and it looks like it downloaded, it shows "Enabled", Design Extender Version 1.2.1. I now see a "Site Assist" tab in my Dreamweaver, but when I click on ANY of the options (including Site Importer, which is the only one I need), nothing happens, no error message, nothing at all. I tried to uninstall Design Extender, go back and reinstall Site Import...but now it's asking me for that serial number...but I don't have that (can't find it) and when looking at my account on your site I only see Design Extender and that serial number. Please help.