It should be in the config for the jukebox (MP3) that you force the rescan of folders.
I open MA and goto config for mp3/jukebox, 1st selection is path to my jukebox software which is now SKjukebox but then the option under scan is greyed out so I cant force a rescan. When MA starts I have mame & Jukeade to choose from..have even tried to overwrite the jukebox png in MA folder but still keeps showing jukeade not my installed jb software.
In mame (through MA) I can't get it to show my faves ini, or even list just my roms.

Thinking of doing a new clean install to try iron out the bugs.
