What was found
AFTER TO ON FLIGHT 3353, LANDING GEAR HANDLE WAS SELECTED UP, LANDING GEAR FAILED TO RETRACT. GEAR UNSAFE LIGHT REMAINED ILLUMINATED, AND HYDRAULIC PUMP CONTINUED TO RUN. AIR RETURN TO BUF. MAINTENANCE CLEANED CANNON PLUGS AND UPLOCK SWITCHES, PERFORMED OPS CHECK. ALL SYSTEMS CHECK NORMAL.