If I understand how it works, it loads the editor from your WordPress into a text widget. Based on their plugin page, this is part of their description:
This plugin adds a WYSIWYG text widget based on the standard TinyMCE WordPress visual editor.
I’m going to guess you thought it would load in an advanced TinyMCE editor that is different? If so, you would also need to add the TinyMCE advanced plugin, which it would then load that in the widget.