I had to uninstall and reinstall both CC 2015 and then Extension Manager... Then I had to completely uninstall all of the extensions that were still listed but not installed before it started working for me again.
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.