Toriaz sp16

Hi, I’ve recently purchased a sp16 and have done the latest update , everything is great except when I try to load samples from a usb they appear to not be there.They are sowing on my Mac as wav files but when I put in the usb and click the image opens but is empty .Ironicly all the tricky stuff I thought would take a lot of learning is easy but this simple procedure is proving a stumbling block , what am I doing wrong please