As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMBOUT, MASTER DOOR WARNING LIGHT ILLUMINATED AND AIRCRAFT WOULD NOT PRESSURIZE, ACCOMPLISHED AIR TURNBACK. INSPECTED CARGO DOOR LATCH SYSTEM AND FOUND THE LEFT LATCH DOES NOT GO TO FULL OVER CENTER AND LATCH. RECYCLED CARGO DOOR AND VERIFIED DOOR CLOSED AND LATCHED TRANSFERRED ITEM TO DMI PER MEL 52-3.