Hello Robert,

Have you tested this on another browser?

Does it work on Google Chrome, Edge, Opera, Vivaldi, Avant, Brave, or the other browsers, or have you tested it only on Firefox?

If it is an issue on all browsers, then Audible is at fault for this, and there is most likely nothing you can do about it.

Happy browsing!

Please explain the problem in detail. What happens? What is/are the exact error message(s) ?

Go to the Mozilla Add-ons Web Page {web Link} (There’s a lot of good stuff here) and search for a download manager.

This download manager works separately from the browser. The browser tells it what to download, and off it goes.

http://www.freedownloadmanager.org It is a powerful modern download accelerator and organizer for Windows and Mac.

Try to change the file extension to .aax if it is currently saved by Firefox as .mp4. If Windows hides the .mp4 file extension then make sure to enclose the full name in quotes ("audiobook.aax") or make sure you see the full name.