can't relock bootloader and stuck

I'm trying to go back to stock from CM12.
I tried flashtool to flash a stock image, and after I selected relock bootloader.
it says it's gone OK, but stock doesn't boot after.

If I go back to flashtool, and I select BLU, it gives me the option to relock the bootloader! I thought it was locked already.

what can i do?

thanks