Registering / Un-registering the device disturbs the "Kindlet related" parts of the overall jailbreak (the one that allows you to run our Kindlet applications). The "Device Jailbreak" survives (the one that lets you install our packages).
Your re-installing the "prerequisites" **after** the change in registration was the correct step to take. It should have fixed that error message.
My **guess** is somewhere, something is cached - -
So now try a full re-boot of the system (press and hold power switch for 20 seconds or more).
OOPS - twobob types faster than I do - but both answers apply.