As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON CLIMBOUT ACFT FAILED TO PRESSURIZE CABIN PRESS WARNING ILLUMINATED. ALL CHECKLIST WERE COMPLETED. ACFT STILL FAILED TO PRESSURIZE IN AUTO AND MAN MODES. FLT CONTINUED UNPRESSURIZED. PLACED ON MEL. MEL CLEARED BY REMOVED AND REPLACING AFT CARGO DOOR SEAL AS PER Q400 AMM TASK 52-31-26-000/400-801. AIRCRAFT WAS PRESSURIZED TO 5.0 PSI. NO DEFECTS NOTED, RETURNED TO SERVICE.