Have you seen the correct log? Mine fails when executing a game, in this log, a Master System one:
[2017-01-22 13:15:15] [ERROR] [Launcher] Failed to run: Z:\Super DreamStation Plus\RetroFE 0.6.169\collections\launchers\Fusion\Fusion36\Fusion.exe
(My launchers are on the default folder, without changing the path on any settings.conf)