Can't unlock bootloader

I recently discovered that my phone had already lost its DRM keys (purchased the phone second hand). So I decided I wanted to unlock the bootloader to install the DRM fix to see if that improves my camera quality.

I have followed all of the guides I can find and have attempted to troubleshot it, however nothing seems to be working.

This is the error I am getting:

Code:

---

C:\Flashtool\x10flasher_lib>fastboot -i 0x0fce oem unlock 0xKEYHIDDEN
...
FAILED (remote: Command did not succeed)
finished. total time: 0.022s

C:\Flashtool\x10flasher_lib>fastboot -i 0x0fce oem unlock 0xKEYHIDDEN
...
FAILED (remote: Device is already rooted)
finished. total time: 0.004s

C:\Flashtool\x10flasher_lib>

---

I have tried creating a folder in the flashtool folder with my device id and ulcode.txt with the unlock code in it, same result.

Any suggestions on what I could be doing wrong?