K4 KUAL not launching on Kindle 4 Non-Touch (fw 4.0.1) after jailbreak – need help

[Task]

Hello everyone,

I have a Kindle 4 Non-Touch with firmware version 4.0.1 (1331440003). I bought it used, and I noticed it already had jailbreak files on it. To test if the jailbreak was working, I successfully installed a screensaver hack (the file was already on the device, named differently).

After that, I wanted to install KOReader. I learned I need MKK and KUAL first. Here's what I did step-by-step:

1. First attempt: I installed an MKK version from 2014 and then a newer KUAL. KUAL did not launch. I then installed DevCerts from 2025, but that didn't help either.
2. Second attempt: I manually deleted all the KUAL and MKK files from the Kindle via PC (without using any uninstall files).
3. Third attempt: I installed the newest MKK (2025) and KUAL again. KUAL still does not start.

Now, when I try to open KUAL, the Kindle shows an error message: "The selected application could not be started. Please try again." (or a similar "Application Error").

Important notes:

· Wi-Fi has been off since the beginning, so no OTA updates were installed.
· The Kindle is not registered with Amazon.

My questions:

· I wanted to update my Kindle through My Amazon, but apparently the jailbreak won't let me do this. Should I remove this jailbreak and install a new one, or reset to factory settings? I'm afraid because I've read that this could turn my Kindle into a brick. What do you advise?

Any help is greatly appreciated. Thanks!

[Frogm4n]

The old certs have expired and you need to update the firmware to 4.1.4 for the 2025 Dev Certs to work.

It's not likely the jailbreak blocking update, as the old K4NT needs to be updated step-wise to get to the latest version.

https://www.amazon.com/gp/help/custo...DD8E64F7AAEF8A