[jhowell]

Originally Posted by innocenat

I put the entire log up here : https://pastebin.com/d0V10giG (hope this doesn't violate the rule). The book in question is not in public domain.

Thanks for supplying the log. There is no problem with posting that here since you are not asking for assistance with DRM removal.

It appears that the Kindle Previewer is emitting an empty mime type field for the cover image which is something that I have not encountered before. It may be a difference with how it works under MacOS vs. Windows. I will change the KFX Output plugin so that it will not fail in this case.

The change will be in the next plugin release which I plan to have out sometime in the next week. Hopefully that will resolve the problem.