As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DFW TO IAH - ON TAKEOFF, THE CREW RECEIVED A "LG AIR/GND FAIL" MESSAGE AND THE LANDING GEAR WOULD NOT RETRACT. THE AIRCRAFT LANDED BACK AT DFW WITHOUT INCIDENT. MAINTENANCE INTERROGATED THE CMC AND FOUND A MESSAGE FOR A PROX SWITCH FAIL. AFTER INSPECTING THE PROX SWITCHES, A CONNECTOR WAS FOUND LOOSE. AFTER TIGHTENING THE LOOSE CONNECTOR AND RESETTING THE AIRCRAFT'S POWER, THE AIR/GROUND MESSAGE DISAPPEARED AND DID NOT RETURN.