I'm still struggling with getting my music on a usb drive. I finally got fed up and emailed Uconnect Customer care. Maybe this will help someone else. Here was their reply:
"I am more than happy to provide you with information as much as I can. In regards to your iPod classic, we unfortunately do not have a list of iPod devices supported. iPods are considered plug and play devices depending on the generation of iPod as newer generations have Bluetooth capability. Disconnecting and reconnecting device is the only trouble shooting for iPods.
In regards to having music within a USB drive, all music must be in .mp3 or .WMA format. Music from iTunes is not always compatible even if the music file has been converted into .mp3 format. Music must be in 8 folders with no more than 255 songs in each folder.
For Apple Car Play, we do not have many trouble shooting options. However, within the settings of the phone you can remove the vehicle to restart the connection. Settings -> General -> Carplay -> Uconnect. Click Uconnect and then click forget vehicle. "
So for the people that are using the usb drives, only 8 folders and 255 songs per folder? Is this what everyone is doing? 2040 song limit?
As for the Apple Car Play, mine will come up button the buttons on the 12" display freeze up and won't do anything. It usually will work through the phone. Kinda defeats the purpose of having it on the screen if you can't control it though.