I sought the help of my son. He has explained why I am encountering the issue. Consequently, I no longer have a problem.
The solution (for me as least) was as follows; when I used the clipper I was clipping only a portion of the visible screen. Therefore the clip only showed the portion I had clipped and the left the rest of the screen black. I was expecting to see the portion that I had clipped appear as a full screen clip and was flummoxed when it only showed a part of the visible screen . Once I went back to the clipper and expanded the section visible on the screen so that the p