As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT 5202 - EN ROUTE DCA-BOS RECEIVED A LEFT PACK OFF FAIL STATUS MESSAGE AND PRESSURIZATION PROBLEM, CREW DECLARED AN EMERGENCY AND DIVERTED TO PHL. FLIGHT LANDED WITHOUT INCIDENT. REPLACED UPPER DUCT FOR THE LEFT AIR CONDITIONING PACK.