Aux problem with usb/mp3 player

[perak]

heloo

i just bought xcarlink and i have strange problem. When i put an usb key in to xcarlink it doesnt happen anything, it is acting like it is no media available, or it show on display like its playing something, but there is no sound, but when i put sd card in to slot it works normaly.

its mazda 3 2004 with ordinary radio, no cd.

i have changed 3 xcarlink, and it always the same

has anyone got any idea.

thanks

peter