As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
IAD - FLT 2808 - ON CLIMB OUT FROM IAD, AIRCRAFT WOULD NOT PRESSURIZE IN AUTO OR STANDBY MODE. FLIGHT RETURNED TO FIELD AT IAD AND LANDED WITHOUT FURTHER INCIDENT. NO EMERGENCY WAS DECLARED. MAINTENANCE ACCOMPLISHED CABIN PRESSURE CONTROLLER FUNCTIONAL TEST AND FOUND FAULT IN CONTROLLER. REMOVED AND REPLACED CABIN PRESSURE CONTROLLER. OPERATIONAL CHECK GOOD PER MM 21-31-0A. (X)