As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING TAKEOFF POSITIVE RATE CALLED FOR LG UP. FIRST OFFICER RAISED GEAR HANDLE UP. LG DID NOT RETRACT & THREE GREEN LIGHTS STILL ILLUMINATED. TURNED THE AIRPLANE BACK TO THE AIRPORT LOWERED THE LG HANDLE IN DOWN POSITION & LANDED AT AIRPORT.