As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SHIP 3719 - ATB - DURING FLIGHT AT FL 360 THE CABIN ALTITUDE LIGHT ILLUMINATED. LEFT DUCT PRESSURE 10, RIGHT 40. AIRCRAFT RETURNED TO MCO. PERFORMED LEFT ENGINE PNEUMATIC HEALTH CHECK. BAR FAILED. REPLACED #1 BLEED AIR REGULATOR. PERFORMED SINGLE PACK CONFIDENCE CHECK AND LEAK CHECK ON BOTH PACKS. CHECKS GOOD.