As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AN OPERATOR EXPERIENCED A PRESSURIZATION ISSUE, THERE WAS NO RESPONSE FROM THE PRESSURIZATION SYS, EITHER IN AUTO OR MANUAL MODES, AS THE ACFT WAS CLIMBING. AT THIS POINT, THE CREW ELECTED TO DO AN AIR TURN BACK AND COMPLETED AN UNEVENTFUL LANDING. TROUBLESHOOTING FOUND, CDS MESSAGE: "CPC/OF VALVE DATA FAIL" MESSAGE. OPERATOR REPLACED THE OUTFLOW VALVE AND THE ACFT WAS RETURNED TO SERVICE.