"Why are you trying to update the firmware?"
I always ask this question too. Does this FW correct something you need or do? If it doesn't you may not even see a difference in camera operation with the FW update. If it has a bunch of bug fixes it is well worth doing but find out what it does first.
Did you format the SD first and then load the FW file on it? Best is all by itself.
EB
EOS 1DX and many lenses.
