As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW REPORTED LT PACK DID NOT PRESSURIZE AND LT PRESSURE REGULATING SHUTOFF VALVE DID NOT WORK AFTER TAKEOFF. CREW RETURNED TO FIELD AND LANDED WITHOUT INCIDENT. MAINTENANCE INSPECTED, R & R TENTH STAGE SHUTOFF VALVE AND PERFORMED CHECKS IAW AMM. ACFT RELEASED FOR SERVICE.