Sansa Fuze player doesn't work when plugged into car via USB?

I know the USB slot works because I have played a different USB drive with music several months ago and that worked just fine.

So I don’t think it’s my player but the car says “No files.” But obviously there IS music in the player so not sure why it’s not working.

It’s an 87 Mercedes if that matters.

Does it make a difference which format? My music files are in ogg format.

Can someone help me out please? Thanks!