Not able to lock bootloader again!!

i have a xperia z1 and i am not able to lock the bootloader again
LOGS
31/019/2016 21:19:58 - INFO - Flashtool Version 0.9.18.6 built on 30-05-2015 22:30:00
31/019/2016 21:19:58 - INFO - Executing search strategies to find proxy selector
31/019/2016 21:19:58 - INFO - No proxy found for IE. Trying next one
31/019/2016 21:19:58 - INFO - Strategy firefox failed trying next one : No Firefox installation found
31/019/2016 21:19:58 - INFO - No proxy found for java. Trying next one
31/019/2016 21:19:58 - INFO - Syncing devices from github
31/019/2016 21:19:58 - INFO - Scanning devices folder for changes.
31/020/2016 21:20:03 - INFO - Pulling changes from github.
31/020/2016 21:20:05 - INFO - Devices sync finished.
31/020/2016 21:20:07 - INFO - Please connect your device into flashmode.
31/020/2016 21:20:09 - INFO - Device connected in flash mode
31/020/2016 21:20:09 - INFO - Opening device for R/W
31/020/2016 21:20:09 - ERROR - root : this bundle is not valid
31/020/2016 21:20:16 - INFO - Processing loader.sin
31/020/2016 21:20:16 - INFO - Checking header
31/020/2016 21:20:16 - ERROR - Processing of loader.sin finished with errors.
31/020/2016 21:20:16 - ERROR -
31/020/2016 21:20:16 - INFO - Your phone bootloader cannot be officially unlocked
31/020/2016 21:20:16 - INFO - You can now unplug and restart your phone

Any Idea ??

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