As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AC WILL NOT PRESSURIZE IN AUTO OR MANUAL MODES-C/A-FOUND GROUND CONNECTION FLAP-TYPE CHECK VALVE MISSING. BOROSCOPED MAIN DISTRIBUTION MANIFOLD AIR-DUCT, NO DEFECTS NOTED. REMOVED AND REPLACED FLAP-TYPE CHECK VALVE IAW AMM 21-22-04. PERFORMED PRESSURIZATION OPC IN AUTO AND MANUAL MODE IAW AMM 22-31-00. OPC GOOD NO FURTHER DEFECTS NOTED.