As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DFW - CREW REPORTED NO PRESSURIZATION DURING TAKEOFF. EMERGENCY DECLARED FLIGHT RETURNED DFW LANDED WITHOUT INCIDENT. AIRCRAFT REMOVED FROM SERVICE. RE-SECURED LOOSE ELBOW CONNECTION ON RIGHT PRESSURE REGULATOR VALVE. SYSTEM GROUND CHECK NORMAL OPERATION.