As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CLT - FLT NR 0690 - THE AIRCRAFT DID NOT PRESSURIZE AFTER TAKEOFF. THE CAPTAIN DECIDED TO RETURN TO CLT. NO EMERGENCY WAS DECLARED. MAINTENANCE REPLACED THE AIR CONDITIONING S/O RELAY AND THE RATE CONTROL VALVE. REFERENCE NR USAA950896.