I've been getting this error at all of my attempts to convert books into KFX.
https://i.imgur.com/sm6pYWH.png
I just noticed this after I updated to Calibre 5.9. I then uninstalled it and tried several versions (starting in version 4.20) but it didn't work. Kindle previewer was on version 3.48, I thought updating it might fix the issue. I went on and updated it to version
3.50, yet the problem persists, which leads me to think this is a problem with the plugin.
Any ideas on how to solve this issue?
EDIT:
Just as an addendum to my last post, all the books I converted up until like, 2 weeks ago, are also being met with the aforementioned error.