As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) UNABLE TO PRESSURIZE CABIN. AIRBORNE RETURN. RESOLUTION - SKIN AIR OUTLET VALVE REPLACED IAW AMM 21-26-53-PB401. AVEC COMPUTER REPLACED IAW AMM 21-26-34 PB401, AND NEW DUCTS INSTALLED IAW AMM 21-26-42-401. CARRY OUT OPS TEST OF THE VENTILATION SYS OF THE AVIONICS EQUIPMENT AMM TASK 21-26-00-710-001-A.