It looks like you installed an older version not compatible with CC 2015. Completely remove the extension from extension manager and download and install the latest version from our web site and that error should go away.
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.