As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT NR 5207 (LAX/SMX) PILOT REPORTED THAT AFTER TAKEOFF THE LANDING GEAR WOULD NOT RETRACT. THE THREE GREEN GEAR INDICATIONS AND THE HYDRAULIC FLUID PRESSURE WERE NORMAL. THE AIRCRAFT RETURNED TO FIELD. MAINTENANCE FOUND THE EMERGENCY GEAR RELEASE VALVE RESET PIN POPPED. MAINTENANCE REPLACED THE SELECTOR VALVE. THE OPERATIONAL CHECKS WERE GOOD. THE AIRCRAFT WAS RETURNED TO SERVICE.