As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) L PACK HI PRESSURE OCCURRED SHORTLY AFTER TAKEOFF QRH PROCEDURE PERFORMED WITH NO SUCCESS AND APU WAS USED TO PRESSURIZE CABIN. RETURNED TO FIELD CORRECTIVE ACTION: REMOVED AND REPLACED LH PRSOV IN REFERENCE TO AMM 21-51-43. (TC# 20191007011)