As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW REPORTED RECEIVING A LANDING GEAR AIR/GRD FAIL MESSAGE ON THE EICAS. MAINTENANCE INSPECTED AND FOUND A TORN AND ROLLED O-RING IN THE NLG STRUT. REPACKED THE NLG STRUT IAW CMM FOLLOWED BY SEVERAL SUCCESSFUL GEAR EXTENSION AND RETRACTION CHECKS.