As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
JFK - CREW REPORTED AFTER TAKEOFF UNABLE TO PRESSURIZE CABIN. EMERGENCY DECLARED FLIGHT RETURNED JFK LANDED WITHOUT INCIDENT. FOUND LOWER HINGE ARM FLAPPER SEAL STUCK PREVENTING LEFT NUMBER 1 DOOR FROM SEALING. REPOSITIONED FLAPPER SEAL. SYSTEM GROUND CHECK NORMAL OPERATION.