As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) DURING CLIMB CREW NOTICED PRESSURIZATION WAS NOT WORKING AND DECIDED AN ATB. MAINTENANCE PERFORMED FUNCTIONAL TEST OF PRESSURIZATION SYSTME BUT WERE UNABLE TO REPRODUCE THE FAULT. A/C RETURED TO SERVICE. MONITORED NEXT 6 FLIGHTS, THE FAULT DID NOT REOCCUR.