Why copy-paste is not working?

If you’re not able to use keyboard shortcuts for copy-paste, try selecting the file/text using your mouse, then select “Copy” and “Paste” from the menu. If this works, it means that your keyboard is the problem. Make sure your keyboard is turned on/properly connected and that you’re using the right shortcuts.

What to do when copy-paste is not working in Android?

2) ROOT your device, install ROOT Explorer, navigate to / > data > clipboard, select ALL and delete all, than go into your Settings > Applications Manager > All, look for TestServices, than remove updates/clear data. Reboot and everything should be fine.