As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW RECEIVED AN AFT CARGO DOOR WARNING INDICATION. CREW LEVELED OFF AT 10,000 FT, CABIN WAS NOT PRESSURIZING AND CREW ELECTED TO RETURN. AN EMERGENCY WAS NOT DECLARED AND LANDED WITHOUT INCIDENT. ON ARRIVAL, MX FOUND DOOR HANDLE WAS IN THE OUT POSITION. MX INSPECTED THE DOOR AND LATCHED/UNLATCHED NUMEROUS TIMES IAW AND OPS CHECKED GOOD. ACFT IS GOOD FOR SERVICE.