DJM-900NXS2 USB problem

Hi everyone, I've recently bought the mixer and had no issues until today. I woke up and turned it on (it was turned off with the button and no usb connected). I connected my usb cable to the port A, and I'm using traktor in my macbook. I've been using it like this for like a month but today when I tried to play a song, there was no incoming signal from the PC (no led from volume lighted up). So I started going through traktor configuration to see if there was anything that produced the problem. Unfortunatelly everything was ok, so I restarted traktor, as with my computer and DJM. Same thing, music is being played of course, and if I dont use the mixer, it goes out through my pc speakers. As I have 2 usb ports in the DJM, tried to plug it in the B one, and it works. Also channels were set to port A, and when switched to B, I changed them. So I'm guessing that the problem comes from hardware? Any help? Thanks