why does my magic mouse button and scroll surface not work?

My MacBook Air 13" ran out of power before I could connect it to a power source. After I was able to power it on again, the Magic Mouse button and scrolling surface could no longer work even though I could still use the optical pointer below to move the cursor. How can I restore the button and scrolling surface. Have tried powering down and up both the MacBook Air as well as the mouse. Also tried unpairing and re-pairing both but nothing works so far. Thanks.