As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ENROUTE, RECEIVED CABIN ALT CAUTION MSG. FOLLOWED QRH, DID NOT PRESSURIZE IN AUTO OR MANUAL. ACFT DIVERTED AND LANDED SAFELY. AFT CARGO DOOR WAS FOUND AJAR, RESECURED AFT CARGO DOOR. NO FAULTS FOUND IN MDC, OPS CHECK OF PRESSURE SYS GOOD.