As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON FLIGHT 3793 THE CREW REPORTED THAT ON TAKEOFF THEY WERE UNABLE TO PRESSURIZE IN AUTO OR MANUAL MODE. THE AIRCRAFT RETURNED TO ORD. THE AIRCRAFT WAS REMOVED FROM SERVICE. FOUND GROUND VALVE IN PARTIAL OPEN POSITION. FULLY CLOSED THE OPERATIONAL AND PRESSURIZATION SYSTEM CHECKS WERE GOOD PER CRJ 700 AMM, 21-31-00. THE AIRCRAFT WAS RETURNED TO SERVICE.