Unhappy Sony Xperia Z ultra - Fastboot FAILED (remote: Command not allowed)

Dear all,
I am new in here because I have a problem with my Sony Xperia z ultra, I receive an error every time I was trying to use Fastboot flash boot adv-stock-v4.img. And the error is:

FASTBOOT Output:
sending 'boot' (16800 KB)...
OKAY [ 0.547s]
writing 'boot'...
FAILED (remote: Command not allowed)
finished. total time: 0.550s

Please someone helps me for this problem.
Note: ADB and Fastboot drivers are already recognized.
Thank in advance.