UZ2315H - Only one speaker is working (?)

Hi,

I've just got my new monitor, UZ2315H.
I connected it to my desktop via HDMI.
I've also connected it via usb in order to enable the speakers too.

The problem is that i hear the sound from one speaker only (bottom left).
As the monitor has 2 speakers, i guess that the other one is at the bottom right. But i can't hear any sound from it. The sound only comes from the bottom left side.

What can i do? Should i send the monitor as DOA? Or do i miss something?

Thanks in advance.