As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DISCREPANCY: AFTER TAKEOFF THE LANDING GEAR FAILED TO RETRACT, PILOT RETURNED TO BASE AND CONDUCTED AN OVERWEIGHT LANDING ( LANDING WEIGHT 69.5 VREF 152+5=157). CORRECTIVE ACTION: PERFORMED FAULT ISOLATION OF PRIMARY LANDING GEAR TRANSFER VALVE. FOUND ALT EXTENSION ACCESS DOOR IMPROPERLY STOWED. PERFORMED PSEU BITE CHECK AND TEST OF MLG. NO FAULTS NOTED.