As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT RETURNED TO FIELD WHEN AFTER TAKE-OFF, AND DURING THE CLIMB, THEY WERE UNABLE TO PRESSURIZE THE AIRCRAFT. MAINTENANCE INSPECTED THE AIRCRAFT AND FOUND THE BLOW OUT PANEL DISLODGED. THE PANEL WAS RESEATED AND OPERATIONAL CHECKS WERE PERFORMED. THE OPERATIONAL CHECKS WERE GOOD AND THE AIRCRAFT WAS RETURNED TO SERVICE.