As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMBOUT ABOVE 10,000 FEET, UNABLE TO CONTROL CABIN ALTITUDE IN EITHER AUTO OR STANDBY. AIRCRAFT RETURNED TO MSP, FUEL WAS DUMPED, AND LANDED WITHOUT INCIDENT. REPLACED CABIN AUTO PRESSURE CONTROLLER AND PERFORMED OPERATIONAL CHECK. CHECKED OK. ALSO PRESSURIZED AIRFRAME AND CHECKED FOR LEAKS.