unable to paste screenshots using Command C?

Hi, I was always able to take screenshots (Command +Opt + Shift +4) and then directly paste them into mac mail emails or Messages using Command + C. Lately I am not able to, perhaps since 10.11.4? I am still able to take the screenshots but am unable to paste them. They now end up on my desktop and I have to search for them and then drag and drop which is a slower process than before. I am also noticing the same problem in photoshop CC 2015, that I can no longer directly paste screenshots but have to drag and drop them from the desktop.

I don't know what is causing this. Is anyone else experiencing this and is there a way to fix it?

Thanks for your help.