If your device claims that it's not a test device, it just means that your kindle does not have CR3 development keys installed, some time ago each developer created their own key and JB just adds KUAL key to a keystore. New version of CR3 uses standard KUAL key *I think (info Merged Developer Keystore
https://www.mobileread.com/forums/sho...d.php?t=152294)
You could add them but I suggest updating your CR3, your JB or using another version of CR3 (for example CR3 + Games and stuff
https://www.mobileread.com/forums/sho...d.php?t=229288 this one works on KUAL 100%)