why is my copy and paste not working?

just check this one

Disable "Overscroll" in the tools preference settings.

Had the same issue. Fixed it by turning Num Lock off and on. I am not sure why this happens but y'all could try that.

@rcleonard, you have posted in the Photoshop Elements forum, not the Photoshop CC forum.  You should repost in what is now called the Photoshop ecosystem forum. 

Same problem. I tried the same routines. Photoshop Elements just quit working properly. All of Adobe's software products are filled to the brim with glitches. I quit using their products after 10 years, swearing I'd never use them again. But here I am. Just shoot me.

import from camera wrote: I have been trying to copy and paste part of an image into a new background.

Try the following and let us know if this works for you:

In Editor, go to the expert tab.

1. Open picture B, the one you wish to select something from to add to another picture.
2. Use one of the selection tools, e.g. selection brush, lasso tool, to select the object. You will see an outline ("marching ants") once the selection is complete
3. Go to Edit menu>copy to copy the selection to the clipboard
4. Open picture A, then go to Edit>paste
5. Use the move tool to position object from picture B.
6. In the layers palette you should see picture A as the background layer, and object B on a separate layer.