As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LOST PRESSURIZATION AT FL 260. COMPLIED WITH QRH, A/C DID NOT PRESSURIZE AUTO OR MANUAL. TROUBLESHOT TO LT PAC S/O VALVE INOP. PWR TO VALVE. REMOVED AND REPLACED LT PAC S/O VALVE PER SMP. LT PAC OPS NORMAL. PRESSURIZED A/C PER JRH TO 1 PSI DIFF OK FOR SERVICE. R/I FROM FACT PREMATURE REMOVAL/INSTALLATION OFF MFG 398540-2-1.