I have an .epub e-book that was created in 2018. It was tested and worked with Kindle, Apple, and several other readers.
Now, the file does not work in Apple books - and multiple people have tested or complained about this.
I updated the file to make some corrections, and I still experience the error.
The exact error is: "Book Content Unavailable. There was a problem loading book content. Try closing and reopening the book or relaunching the device." (This does nothing.)
But I can take the exact same file and open it in Kindle, Nook app, and two other e-readers I downloaded from the AppStore. They read it without incident.
I created the book in Calibre and ran both the Calibre bug check and the ePubcheck plugin. No errors found.
I have no idea what the problem is, and why it is just Apple. Has anyone else encountered this? Any ideas or guesses?