As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE CREW REPORTED THAT THE NLG WOULD NOT EXTEND DURING NORMAL EXTENSION AND THE NLG WAS MANUALLY EXTENDED AND THE ACFT LANDED WITHOUT INCIDENT. THE GEAR RETRACTION SYS WAS DEFERRED AND THE ACFT WAS FLOWN TO OTHER AIRPORT FOR FURTHER TROUBLESHOOTING. MX FOUND THE SELECTOR VALVE TO BE INOP. THE VALVE WAS REPLACED AND THE GEAR OPERATED NORMALLY.