Have you uninstalled or installed any other extensions recently?
Does the extension show up under the Help->WebAssist menu or does it not get installed there as well?
Do you get any popups or error messages when you are installing the extension?
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.