When you run kunix rgn you only flash boot.bin,fw_all.bin is not inside.
So the problem is in fw_all.bin
Try again with empty SD card and add file that kunix send it to you,maybe you can try also with some other SD maybe with this that you use it is something wrong.
Flash over SD will take about 2min so dont turn off your nuvi.
You can try also disconect nuvi from PC and add SD inside and turn on your nuvi and waith about 2min.