Razer Naga Left Wheel Button (to left / right) not working

I've already updated the Synapse to the latest version. The wheel (middle) button is fine, but when I push the the wheel button to right or left, nothing happens. I tried to assign other functions to the buttons but none of them worked. (My original setting is: right -> Show Desktop, left -> Alt+Left) I even bought a new Naga to replace this one, but the result is the same. I started using this mouse and computer about 3 months ago, everything was fine, don't know since when this happend. Any idea to solve this problem? (Sorry for my English is not very well.)