As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DFW - CREW REPORTED UNABLE TO PRESSURIZE CABIN. FOLLOWED QRH PROCEDURES UNABLE TO CONTROL CABIN ALTITUDE. EMERGENCY DECLARED FLIGHT RETURNED DFW LANDED WITHOUT INCIDENT. AIRCRAFT REMOVED FROM SERVICE. REPLACED ACTUATOR ASSEMBLY FOR FORWARD OUTFLOW VALVE. SYSTEM GROUND CHECK NORMAL OPERATION.