How do I integrate A* with 2D Toolkit's Tilemaps?

I have gone through the getting started guide. I have a separate layer in my tilemap called “Platforms.” The graph’s obstacle mask is set to that layer. I have set the platform tiles up with a polygon collider. When I scan with a ray trace it shows the entire map as walkable. If I scan with a sphere collider it shows the entire map as unwalkable. Any suggestions as to what I am doing wrong?