As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AT DEPARTURE TIME CREW LOST ALL OXYGEN PRESSURE TO ALL MASKS IN THE FLIGHT DECK. SUPPLEMENTAL DATA UPDATE FOUND THAT PRESSURE REDUCING REGULATOR WAS NOT LETTING AIR OUT OF PRESSURE REGULATOR VALVE. REPLACED CREW OXYGEN PRESSURE REDUCING REGULATOR PER MAINTENANCE MANUAL. OPERATIONAL CHECK OK.