Why aren't my custom songs loading on my local R21 machine?

I've put some songs on a flash drive to use at my local arcade. I know for certain that our ITG2 machine is patched to play custom songs of any length because I occasionally play with a friend who has a flash drive that works.

When I plug in my drive, none of my custom songs are loaded, but it does remember my name, modifiers, and personal bests. Why aren't my songs loading?

Things I've tried:

• Every song is a .ogg file
• Every song is less than 5MB in size
• Make sure that every chart is in .sm format, not .dwi or otherwise
• Remove all assets besides the .ogg and .sm file
• Less than 50 songs in the flash drive
• Song folders are all directly in the In The Groove 2/Songs directory
• All songs are less than 2 minutes long
• Remove all but one song from my drive. Even this one song won't load.

Is there anything that I've missed?

One thought that I've had is that I'm trying to prepare my drive using a Mac, and I've noticed that it adds a lot of directories like .Trashes to my drive. I also know that the flash drive is formatted with a file system that Apple computers usually doesn't work with. Is there anything in particular I should be aware of when preparing my drive using a Mac?

I was putting my files onto my flash drive using a Macbook. When I tried again with a new flash drive and running a machine running Windows, my flash drive worked correctly.

Unfortunately, I'm not sure what computers running OSX specifically do that causes problems.