As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON TAXI OUT RECEIVED OVERBOARD EXTRACT VALVE FAULT. FOLLOWED MEL BUT WOULD NOT MAINTAIN PRESSURIZATION IN FLIGHT. DIVERT TO ATL PER GOC. ACN RELEASED FOR SERVICE PER MEL/CDL: 21-23-06 CATEGORY: C. VENT OVBD VALVE INOP, VALVE MANUALLY SET PARTIALLY OPEN, FOR GROUND OPERATION OF AVIONICS, CONDITIONED AIR MUST BE AVAILABLE AND USED." REMOVED AND REPLACED OVBD EXTRACT VALVE PER MM 21-23-13-4. OPS CHECKED NORMAL.