DJM 350 usb recording problem

Hi, i'm choi who use 'djm-350' with usb recording system.

i was always record my mixset with usb port but few days ago, 'wav.' file is not saving in my usb. I also changed new usb and checked new wav. file, but also there was no any recorded file. 

in DJM350, when i put usb in usb port the red light is work ordinary and also recording is working(I can hear in djm350). but the problem is wav file is not produced in usb.

please help me....