@LadyKate: Can you make sure you have the latest version of the plugin installed. This is 1.3.12.
If that doesn't help, delete the saved settings for the plugin. To do this, open the calibre preferences, go to the "Miscellaneous" section and press the "Open calibre configuration Then go into the directory "plugins" and find the file "Modify ePub.json" and delete it. The restart calibre and try the plugin again.
|