As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF, LEFT PACK CONTROL VALVE WOULD NOT MAINTAIN CABIN ALTITUDE OF 1000 FEET WITH AIRCRAFT AT FL 250 AND RIGHT PACK OFF. CREW RETURNED TO PHIK AND LANDED WITHOUT INCIDENT. MAINTENANCE VERIFIED SECURTIY OF LEFT PACK/FLOW CONTROL SYSTEM, DUCTS AND COMPONENTS. NO DEFECTS WERE NOTED. VERIFIED SECURITY AND FREEDOM OF OPERATION OF LEFT CONDITIONED AIR, CHECK VAVLE AND RAM AIR(COLD) CHECK VALVE, NO DEFECTS NOTED. MAINTENANCE REMOVED AND REPLACED LEFT FLOW CONTROL VALVE PER ALL APPLICABLE MANUALS.