As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF, CREW REPORTED A LANDING GEAR AIR/GROUND FAIL MESSAGE ON THE EICAS AND THAT THE LANDING GEAR WOULD NOT RETRACT. MAINTENANCE INSPECTED THE AIRCRAFT AND CLEANED THE MLG WOW PROXIMITY SWITCHES. A SUBSEQUENT OPERATIONAL CHECK OF THE LANDING GEAR EXTENSION AND RETRACTION SYSTEM PROVED A GOOD FIX AT THAT TIME.