As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
MIA - FLT 1305 - EN ROUTE MIA-SJU -ON CLIMB-OUT NOT ABLE TO CONTROL PRESSURIZATION IN REGULAR 1, REGULAR 2, OR MANUAL MODES. RETURNED MIA AND LANDED WITHOUT INCIDENT. DISCOVERED AIR CONDITIONING CHECK VALVE MISSING AND DOOR OPEN. REPLACED AIR CONDITIONING CHECK VALVE. SYSTEM GROUND CHECKED NORMAL OPERATION. (M)