As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LOSS OF PRESSURIZATION, ACFT DID NOT PRESSURIZATION ON TAKE OFF. AIRCRAFT PERFORMED AN AIR RETURN. MAINTENANCE PERFORMED RESET OF PRESSURIZATION SYSTEM IAW AMM 21-31-00. CLEANED FILTER ON MANUAL PRESSURIZATION CONTROLLER IAW AMM 21-31-02. SYSTEM OPS CHECKED GOOD IN BOTH AUTO AND MANUAL MODE. AIRCRAFT WAS APPROVED FOR RETURN TO SERVICE.