[BookCat]

Hang on a minute chlorine! You're not supposed to put epubs on kindles!

Try converting the news article into mobi format. Kindles are one of the few readers that don't accept epub.

That could be your problem.

How exactly are you sideloading the books?

Plug your Kindle into your usb port.

Go to "My Computer" and open the kindle drive.

In this you should see a folder called "documents". Open this and slide the book into it.

Close the Kindle window.

Go to your task bar and click the "safely remove hardware" icon.

This process assumes:
You're using Windows, and
You have saved the book to your disc drive, rather than sending it from Calibre.

Well, this is how I do it.
Good luck.