As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW REPORTED THAT ON INITIAL CLIMB THE ACFT WOULD NOT PRESSURIZE. THE CREW RETURNED TO FIELD AND LANDED WITHOUT INCIDENT. MAINTENANCE INSPECTED AND FOUND THE OVERBOARD EXHAUST SHUTOFF VALVE WAS NOT DEACTIVATED IN THE CLOSED POSITION. MAINTENANCE DEACTIVATED OVERBOARD EXHAUST SHUTOFF VALVE, PERFORMED CHECKS IAW THE AMM AND THE ACFT WAS RELEASED FOR SERVICE.