As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE FLIGHT CREW REPORTED THAT THE AIRCRAFT FAILED TO PRESSURIZE ON DEPARTURE IN BOTH AUTO AND MANUAL PRESSURE CONTROL MODES. THE MAINTENANCE VENDOR DETERMINED A DEFECTIVE REGULATING VALVE AND REPLACED IT WITH A NEW VALVE. OPERATIONAL CHECKS WERE SATISFACTORY AND THE AIRCRAFT WAS RETURNED TO SERVICE