So I have figured out that the problem with the new player is that it doesn’t acknowledge it’s own USB slot. I just synced music to the player itself without a problem.
Synced music the the usb card using the broken player - works fine, but when I take the card to the new player it tells me there’s nothing on the card.
Basically, the new player is straight-up pretending there’s no usb storage. What a jerk it is.