What was found
(CAN) AFTER TAKEOFF, UNABLE TO RETRACT LANDING GEAR. GEAR RECYCLED NO CHANGE. LEFT GEAR NOT UPLOCKED INDICATION ON ECAM COMPUTER. AIRCRAFT RETURNED TO BASE. MAINTENANCE CHECK REVEALED RH GEAR LOCK INSTALLED. LOCK REMOVED, NO FAULT ON CFDS (CENTRALIZED FAULTY DISPLAY SYSTEM). SYSTEM CHECKED SERVICEABLE.