As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIR RETURNED TO DEPARTURE DUE TO A CABIN PRESSURIZATION ISSUE AT OR BELOW 10,000 FEET. VENT SKIN VALVE FAULTED, EXTRACT VALVE POSITION HAD XX DISPLAYED. NO EMERGENCY DECLARED. FLIGHT LANDED WITHOUT FURTHER INCIDENT. AIRCRAFT WAS GROUNDED. MAINTENANCE REPLACED SKIN AIR VALVE PER AMM 21-27-00 AND PERFORMED SATISFACTORY OPERATIONAL CHECK.