As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
MCI - FLIGHT 2647 THE CREW REPORTED THAT THE PRESSURIZATION WENT INTO THE AMBER RANGE DURING CLIMBOUT, AND WERE UNABLE TO REGAIN CABIN ALT OR DELTA P IN MANUAL MODE. THE AIRCRAFT RETURNED TO MCI WHERE IT LANDED WITHOUT INCIDENT. MAINTENANCE INSPECTED THE AIRCRAFT AND CLOSED THE GROUND AIR CONDITIONING FLAPPER VALVE, OPERATIONALLY CHECKED WITH NO DEFECTS, AND THE AIRCRAFT WAS APPROVED FOR RETURN TO SERVICE.