As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
UNSCHEDULED LANDING DUE TO CABIN PRESSURIZATION PROBLEMS. DURING ONE-PACK OPERATION, THE RIGHT FLOW CONTROL VALVE (PACK VALVE) FAILED IN THE CLOSED POSITION. REPLACED RIGHT FLOW CONTROL VALVE (PACK VALVE) THEN PRESSURIZED AIRCRAFT, WHICH HELD PRESSURE.