As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMBOUT THE OVERBOARD COOL CAUTION MESSAGE ILLUMINATED AND THE CABIN DID NOT PRESSURIZE. THE CREW RETURNED TO DAY. MAINTENANCE FOUND THE OVERBOARD EXHAUST SHUTOFF VALVE OPEN. THE SOV WAS SECURED CLOSED IAW CRJ200 AMM 21-24-00-040-806 AND MEL 21-24-06. THE AIRCRAFT WAS THEN RELEASED FOR SERVICE.