saving flight plans using FS flight planner

hey folks i need some assistance with using flight planner as fas as saving a plan to import into the PIC 767. what I do is save the plan and then change the name to an 8 character name such as KBOSKJFK.rte and copy it to the FMCWP folder but when i enter it into the CO route in the FMC and press ACTIVATE nothing happens- what am I doing wrong?