In Order for the Multi-Messager USB to play files correctly they must be named correctly. The naming of your files should be done in the following format:
The File in the first slot of the Multi-Messager must be named "1.mp3" and all other files must be named based on their trigger number, a file in slot 2 should be named "2.mp3" and so on.
Sometimes windows will hide known file extensions and that will cause the file to be named "1.mp3.mp3", if you add an extra extension on it. If the Files are named like this they will not trigger.