What was found
AT FL250 CABIN ALTITUDE EICAS MESSAGE CAME ON, CABIN PRESSURE WAS 10200 CABIN ALTITUDE LIGHT EXTINGUISHED AT AROUND FL200 EMERGENCY DECLARED. FOUND RT CABIN AIR SUPPLY CHECK VALVE DUCT NOT CONNECTED, RED DUCT, ADJUSTED AND RECONNECTED DUCT. PERFORMED SINGLE PACK PRESSURIZATION CONFIDENCE CHECK PHASE II, III, IV. NO LEAKS NOTED. OPS CHECKED GOOD IAW MM 21-51-00.