As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
BOS - FLT 1049 - AFTER TAKEOFF, CREW RECEIVED THE EICAS MESSAGES 'CABIN ALT INOP', 'CABIN ALT AUTO 1' AND 'CABIN ALT AUTO 2'. CREW COULD NOT CONTROL PRESSURIZATION IN MANUAL. FLIGHT RETURNED TO BOS AND LANDED WITH NO FURTHER INCIDENT. MAINTENANCE REPLACED THE OUTFLOW VALVE/ACTUATOR ASSEMBLY. (X)