This may happen when you are trying to preview the course after publishing the course by clicking on the index.html file. In this case the file is launched from the file server and may not work correctly.

It is important to launch the course from the web server, so make sure you put it on web server and then try to fetch the course from there and not by clicking on index.html.

When actually previewing the course from within Captivate, this task is done automatically by Captivate by setting up the webserver on you localhost.