Trying to use a object in SketchUp to trim a componet using Curic Face knife

I just installed Curic Face Knife into SU. I want to use face knife to trim a componet using a rectangle object I have drawn in SU. so I move the rectangle into the componet exactly where I wish to trim the componet.
select the componet click on the Face Knife icon select the rectangle object it selects the whole object including the rectangle and when I right click a trim button appears but when I select it One one side of the componet face knife does not trim anything? what am I doing wrong?

It tells you what to do in the status bar at the bottom of the screen… hit Enter


or in tutorials