Import of demo data fails

I just installed the Kopy theme into a staging/test version of my website. After installing all the required plugins, I went to Appearance–>Theme Options–>Demo Data Import. I kick off the import and it spins for a minute or so, and then I get the following:

Import Error!
An error occurred during the import process.

It appears that the media got imported because I see some of the sample images/icons. However, there are no new pages/posts on the site.

If it makes a difference, this site already has content – it is a full backup of my current production site including themes, plugins, media, comments, posts, etc.

In order to help you investigate this, I am creating an admin ID for you and will send you login details in a private message. Thank you.