As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WE HAD A CARGO DOOR WARNING ON WE CLOSED THE DOOR 3 TIMES AND CHECKED THE VENT DOOR ON THE OUTSIDE AND EVERYTHING LOOKED CLOSED. HOWEVER AFTER AIRBORNE WE LOST PRESSURIZATION AND RETURNED BACK TO THE FIELD. AFTER TOTAL RESET THE CARGO DOOR WARNING REMAINED ON. CARGO DOOR SENSOR HARNESS REPLACED IAW GL6000 AMM 52-31-00-400-801, SPM-WM-20-16-05 OPS TEST C/W IAW AMM 52-31-00.