What was found
CLIMBING THROUGH F230, CABIN ALTITUDE STARTED A 2500-3500 MINUTE CLIMB. SWITCHED TO MANUAL, NO HELP. CABIN CONTINUED CLIMB. PERFORMED DESCENT, MASKS FELL. LANDED UNPRESSURIZED. NO DOOR LIGHTS NO OTHER UNUSUAL WITH A/C PERFORMANCE. FOUND CARGO DOOR SEAL BLOWN OUT ON LOWER SIDE OF CARGO DOOR. REPLACED BENT RETAINING STRIP FOR CARGO DOOR SEAL.