What usually works is to disable the option on both LW and iTunes, then re-enable the settings on both. For iTunes that means Preferences -> Advanced -> Copy files to iTunes Media folder when adding to Library. However the problem is usually LW related.
LW's menu bar, Tools > Options > My Files > iTunes (Configure).
You may need to restart both iTunes and LW for the refreshing of the settings to work between the two programs.
iTunes sometimes stops importing files from LW when LW has been running a long time. Java related at a guess. If that's the case, simply restarting LW and iTunes may fix the issue.