As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DIVERSION/ DECLARED EMERGENCY. LEVEL AT FL400 ALT WARNING HORN SOUNDED. SPLIT DUCT PRESS VALUES 20 AND 40 PSI, NO WARNING LIGHTS. CABIN CLIMB 1500 FPM AT THE MAX POINT. MASKS DID NOT DROP. FOUND NR 1 ENGINE BLEED INOP. REMOVED AND REPLACED NR 1 ENGINE PRSOV AND NR 1 ENGINE HIGH STAGE VALVE PER MM.