Please see the photos below. I used the rectangular marquee tool to select the portion of the white backdrop to the right of the little boy in order to extend the background fully to the right frame of the photo. You can see that the only dashed lines representing the outline of the selection are visible on the lefthand border and on the bottom border. There is no visible righthand dashed-border with which to transform/extend the white background fully to the right.
You can see from the other two photos that, when I place the cursor to the right of the 'virtual righthand border', the cursor is a crosshair. When I move the cursor slightly to the left, moving into the selected area, the cursor changes to a 'move' cursor. So it seems the selection is 'there', but the righthand border is not visible. How do I make it visible?