The following are common causes of this issue.
- The "Web Site URL" or "Application Path" settings in your control panel are incorrect, which is causing the required Javascript files to not be included. Please check this setting in your control panel under Settings -> Website Settings. If the dropdown issue is preventing you from accessing this section of the control panel, you may access your control panel directly by pointing your browser at:
http://www.yourwebsite.com/admin/index.php?ToDo=settings (the actual path to the control panel index.php will change depending on your sites installation).
The values for both fields should follow these examples:
Web Site URL: http://www.example.com/articles
Application Path: /articles/
Once you have corrected one or more of these issues, be sure to clear your browser's cache for the changes to take full effect.