mobile

I'm trying to unlock the bootloader of my One M9 so that I can use Sunshine and get S Off. In the end I'm trying to convert it to the dev version. I've unlocked the bootloaders of my M7 and M8 before this but for some reason it is giving me an error this time. It says "FAILED (remote: unknown command)" every time I try. I've tried with sync manager install and uninstalled. I really have no idea why this is happening. I tried to get the tokens on the M7 and M8 with the same drivers to test them and everything went as usual. Can anyone help me with this?

Thanks