Clipboard stopped working

Found a solution here

Run the following: cmd /c "echo off | clip"

You can even make it into a desktop shortcut if the problem keeps happening.

For me the problem was happening only when there was a RDP session open to another machine. After closing RDC, clipboard started working again.

There's probably an app that's "locked" the clipboard. Try and work out what app has done that and close it.

In my case it was a hung Greenshot.