As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PHL - AFTER TAKEOFF, AIRCRAFT WOULD NOT PRESSURIZE IN ANY MODE OR BLEED CONFIGURATION. RETURNED TO PHL. GENERATED FROM PILOT REPORT. FROUND LEFT OUT FLOW VALVE DIRTY. CLEANED VALVE AREA. OPS CHECK ON GROUND. ALL NORMAL DEFECTS NOTED MM 21-00. (X)