As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMBOUT THE AIRCRAFT WOULD NOT PRESSURIZE. THE CAPTAIN DECIDED TO RETURN TO PIT. MAINTENANCE INSPECTED AND FOUND THE DOOR SEAL DEFORMED AND THE OUTFLOW VALVE BLOCKING TOOL INSTALLED. MAINTENANCE REMOVED THE BLOCKING TOOL AND REPLACED THE DOOR SEAL IN ACCORDANCE WITH DORNIER MAINTENANCE MANUAL 52-00-00. OPERATIONAL CHECKS WERE PERFORMED AND THE AIRCRAFT WAS RELEASED FOR SERVICE.