Dead zones on mousepads are usually dirt or wear.

Usually dirt or a worn-out spot.

The cursor stops responding because the mouse’s optical sensor loses track of the surface. On a mousepad, that happens when a patch gets dirty enough that the light reflects inconsistently, or when the pad’s texture wears down smooth. You see it most often where your hand rests or where you slam the mouse down.

Try cleaning the pad first — mild soap and water, air dry completely. If that doesn’t fix it, flip the pad over and test on a different surface. The dead zone might be the pad itself. In that case, just replace it. They’re cheap enough that you shouldn’t fight a twenty-dollar problem.

A clean mousepad is a happy mousepad.