What was found
THE ACFT DEPRESSURIZED AND WOULD NOT MAINTAIN CABIN PRESSURE, FOLLOWED QRH, DESCENDED TO LOWER ALTITUDE. PASSENGER MASKS WERE DEPLOYED. INSPECTED DOOR SEALS, CHECKED GOOD. PRESSURIZED ACFT IN MANUAL MODE, STABILIZED DIFFERENTIAL AND PRESSURE HELD FOR ONE HOUR WITH NO CHANGES, ON GROUND. PRESSURIZATION CHECK IAW AMM. MANUAL PRESSURIZATION, OPS CHECK GOOD AT THIS TIME.