As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
MIA - AFTER TAKEOFF, COULD NOT PRESSURIZE AIRCRAFT. RETURNED TO MIAMI AND MADE LANDING WITHOUT INCIDENT. PERFORMED OVERWEIGHT INSPECTION. GROUND INSPECTION REVEALED DEFECTIVE OUTFLOW VALVE ACTUATOR. REPLACED ACTUATOR AND GROUND CHECKED OKAY. RETURNED AIRCRAFT TO SERVICE.