Hard to say for certain without the model itself. But, my guess is that the "circle" is not a circle at all. because of the draft there, my guess is that this is not a true circle, but is instead a spline curve, which is why it is filtered out for Concentric. There should, though, be points where the edge seam exists. I'm not sure if a vertical constraint at that point will give you the design intent you are looking for, but it might. Another approach would be to project the bottom edge of that shape into the sketch, assuming that is a circle, and that should allow Concentric to be applied. Again, if we had the model, it would be easier to try a few things.
Jeff Strater
Engineering Director