If the Upgrade Kit returns an "Initialize Flash Failed" error, the NAND chip itself may have reached its end-of-life or suffered a physical failure due to voltage spikes.

Before you attempt any recovery, perform these sanity checks. Skipping this step is the #1 reason people rebrick their radios.

Create a "New" configuration for the exact model and frequency band of your radio. Attempt to this default, empty codeplug to the radio.