[Q] can't unlock bootloader topic

I must start by saying that I'm sorry if this has already been discussed. I've been trying to unlock bootloader on m8 running 3.30 (latest OTA) hbooot 3.19 via HTCDev and when trying to flash unlock code bin. I get:
C:\Android>fastboot flash unlocktoken Unlock_code.bin
target reported max download size of 1826414592 bytes
sending 'unlocktoken' (0 KB)...
OKAY [ 0.125s]
writing 'unlocktoken'...
FAILED (remote: unlock token check failed)
finished. total time: 0.141s

I've copy and pasted and written out the commands: fastboot flash unlocktoken Unlock_code.bin

I've searched several time and multiple websites but haven't found my problem yet any help would be greatly appreciated.