As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CRUISE FROM KBWI TO LPLA THE CREW WAS UNABLE TO MAINTAIN CABIN PRESSURE ON ONE PACK. THE CREW HAD TO DESCEND TO 10,000 FEET. THE CREW LANDED IN KWRI WITHOUT FURTHER INCIDENT. MAINTENANCE REPLACED LEFT FLOW CONTROL VALVE. OPERATIONAL CHECK GOOD IAW DACO MAINTENANCE MANUAL 21-31-0, AND ATI MAINTENANCE MANUAL 21-04-26. AIRCRAFT WAS RETURNED TO SERVICE.