As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMB OUT FROM MSP, THE AIRCRAFT WAS SLOW TO PRESSURIZE. THE CREW CLOSED THE OUTFLOW VALVE, SOME HELP, ALL SWITCHES AND C/B''S NORMAL. CABIN ALTITUDE WOULD NOT LEVEL OFF. OUTFLOW VALVE INDICATION FULLY CLOSED. THE CREW RETURNED TO POINT OF ORIGIN. THE RIGHT FLOW CONTROL VALVE WAS FOUND TO BE INTERMITTANT. REMOVED AND REPLACED RIGHT FLOW CONTROL VALVE. OPERATIONAL CHECKS NORMAL.