As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT NR 770 - ROA - AIRCRAFT WOULD NOT PRESSURIZE AFTER TAKEOFF. OUTFLOW VALVE INDICATED CLOSED IN AUTO, STANDBY, AND MANUAL. RETURNED TO FIELD. MAINTENANCE FOUND AC AND DC CANNON PLUGS DISCONNECTED FROM THE OUTFLOW VALVE. SECURED PLUGS, OPS CHECK NORMAL.