As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW REPORTED A CABIN ALTITUDE AMBER MESSAGE AFTER TAKEOFF AND THE CABIN WOULD NOT PRESSURIZE. CREW ELECTED TO RETURN TO CLT AND LANDED WITHOUT INCIDENT. MAINT REMOVED AND REPLACED THE PRIMARY OUTFLOW VALVE AND THE MAIN CABIN DOOR SEAL IAW THE AC MM. OPS CHECK WERE GOOD. AC WAS RELEASED FOR SERVICE. (K)