Patching a sidewalk or pouring a new one
If one panel cracked and the ground under it is still firm, replacing just that panel can make sense. When several panels have sunk or tipped, the ground underneath has usually moved, and patching the top only puts new concrete back on the same soft dirt. In that case I'd take the walk out, fix the base and pour it new. I'll tell you which one I think your walk needs once I've looked under the edges.

