As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING TAXI OUT FOR FLIGHT 8126 MIA-KIN THE PILOT REPORTED THE LEFT BRAKE WAS INOPERATIVE. THE PILOT RETURNED THE AIRCRAFT BACK TO THE RAMP. THE FLIGHT WAS CANCELLED. THE BRAKE MASTER CYLINDER WAS REPLACED IAW ATR72 JIC 32-42-13 RAI-10000. THE SYSTEM CHECKED GOOD IAW ATR72 JIC 32-42-OPT-10000. THE AIRCRAFT WAS RETURNED TO SERVICE.