As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AS AIRCRAFT CLIMBED THROUGH 10,000 FEET, CABIN WOULD NOT PRESSURIZE. INSPECTION FOUND BOTH FLOW CONTROL VALVES HAD FAILED INTERNALLY. SUBMITTER STATED EXERCISE VALVES MORE FREQUENTLY DURING MAINTENANCE RUNS OR EVALUATION FLIGHTS OR ESTABLISH A TBO OR REPLACEMENT LIFE. (APPEARS NOT TO BE A FLEET PROBLEM).