USB's not recognised on the XDJ-RR

I've recently bought the XDJ-RR, as I wanted a controller that I could play music off of USB's, without the need to bring my laptop with me. I bought the recommended USB's (SanDisk 256GB Ultra Luxe, USB 3.2 Gen 1 Flash Drive up to 400MB/s) but neither are recognised. I've formatted them (fat32) but still, no dice.

An old USB stick I have works with them, but it's not very big capacity.

Any idea on how I can sort this? Thanks.