As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
UNABLE TO KEEP PRESSURIZATION ON AIRCRAFT. QRH WAS RUN. PACKS HIGH, STILL NO CABIN PSI. USED APU AIR NO PSI COULD ONLY GET 1 TO 2 CABIN DIFF PRESS IN AUTO/ALT/MAN BLEED AIR FLEXING 35 TO 42 PSI. NO WARNING LIGHTS CAME ON ALT / OVERHEAT ETC. REMOVED AND REPLACED GROUND CONDITION AIR CHECK VLV PER MM 21-21-01-000-804-002, 21-21-01-400-804-002. OPS CHECKED GOOD. AIRCRAFT PRESSURIZED TO 6 PSI. VLV P/N 69-2914-25.