Commented Unassigned: Paste Buttons Not Working [27925]

I have installed AJAX Control Toolkit 15.1.3 in a Visual Studio 2012 project. I have created a very simple Web page with nothing on it except a single instance of the HTMLEditor control. When I view the Web page, the HTMLEditor appears, but is not working properly. The Paste and Paste from Word buttons are inoperative: clicking them has no effect. Also, the Insert Link button's pop up is completely unlabeled: the two buttons contain no text and the two input fields are unlabeled. Furthermore, there are no tooltips when I hover over the buttons.

Based on this evidence, it seems that an English language pack is missing or misconfigured. What am I missing?
Comments: Would you please attach this sample project to the issue?