I am brand new here and have been teaching myself Inkscape for the past month or so through the many online tutorials. I've run into trouble trying to sharpen a corner that is now rounded. Here's the screenshot:

My goal is to make the corner sharp - I inadvertently made it rounded and don't know how to get back to the sharp corner I had. I'm not really sure what a smooth node handle is - can it be converted to another type? One click changes the square nodes to 'cusp nodes' as well as the round handle nodes report as being cusp node handles. I've tried the "make selected nodes corner" selection from the toolbar. But that only creates a corner from the two square nodes. What am I doing wrong?
I think I've been staring at this too long as the answer is probably right in front of me. I've searched the forum and (I think) the archives, as well as online but haven't been able to find a direct answer to this.