As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) UNABLE TO PRESSURIZE AIRCRAFT ON DEPARTURE. AIRCRAFT RETURNED TO DEPARTURE POINT. MAINTENANCE CHECK FOUND SKIN AIR EXTRACT VALVE INOPERATIVE. VALVE DID NOT CLOSE CAUSING PRESSURIZATION PORBLEM. AVIONICS EXTRACT VALVE COMPUTER REPLACED.