As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APPROXIMATELY FL 310 CABIN PRESSURE EICAS MESSAGE DISPLAYED. MASTER CAUTION OUTFLOW VALVE SHOWED CLOSED. NO CHANGE WHEN SWITCHED FROM AUTO 1 TO AUTO 2. AIR TURN BACK TO PKWA WITH AN EMERGENCY DECLARATION. LANDING WAS UNEVENTFUL ON ARRIVAL, AIRACRAFT GROUNED FOR UNSCHEDULED MAINTENANCE. WORK IN PROGRESS.