As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DEN - FLT 55 - AIR TURN BACK. FLIGHT CREW REPORTED LANDING GEAR WOULD NOT RETRACT. AIRCRAFT RETURNED TO DEN AND LANDED WITHOUT INCIDENT. MAINTENANCE REPLACED LANDING GEAR CONTROL LEVER LOCK SOLENOID. RETRACTED GEAR SEVERAL TIMES AND CHECKED OKAY. TOTAL CYCLES: 1,138. X)