Success! The circuit breaker was not defective. The breaker had two wires coming in both tightened down with a single screw. As I popped the breaker out, one wire immediately came out, not tight at all. The other wire needed a little counter-clockwise action to get it loose. I pulled both wires out and cleaned them, polished them up some with Mrs CMD's Magic Eraser so they were all shiny. I pushed the wires back in, tightened the hold screw, put the breaker back in and Voila! Everything worked perfectly.
Evidently the pounding and hammering when the siding was replaced one wire jostled loose.
Thank you all, got my confidence up to give it a go.