Fastboot commands are not working
I don't know if you are running relock.cmd as a file or a command, but the usual way to lock the bootloader in Fastboot is 

fastboot oem lock


Try    

fastboot devices


And wait until you see your device is found, then do the lock   

fastboot oem lock


Please tell me what errors you get ?



Try also,    


  fastboot flashing lock
        fastboot flashing lock_critical