Also you may want to draw in a new cylinder piece, it looks like the current one you got is maybe a slice out of a longer piece or something? Anyway, it's edge is no longer an exact circle so it is not as easy to get a "cen" snap on it.

If you move the duplicate the edge and turn on control points you can see there are a whole bunch of points in it unlike a regular circle:



So you may want to draw in a new cylinder, or do an extrude of a circle to get a snappable center point on that edge.

- Michael