Resolved! Rather than fighting with the plugin anymore, I inactivated the Zakra Theme and reactivated it. Then I activated the Zakra Child Theme and tried importing again. This time the Book Author Demo imported without any issues.
Thanks for your time!
I used that article to begin with. I already installed the ThemeGrill Demo Importer plugin before I tried to use the Appearance > Demo Importer tool. Just tried again, and it’s the same error message. What else can I try?
