As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT 1808, DCA TO IAH - UPON REACHING CRUISE ALTITUDE THE CREW RECEIVED "CABIN ALTITUDE HIGH" EICAS MESSAGE. THE FLIGHT LEFT DCA WITH NR 1 PACK ON MEL. THE CREW DECLARED AN EMERGENCY AND DID AN EMERGENCY DESCENT PER QRH. THE OXYGEN MASKS DID NOT DEPLOY. MAINTENANCE - TROUBLESHOT SYSTEM, REMOVED AND REPLACED RT CHECK VALVE.