Came across this solution. Found a solution doing a Google search on this issue. Thought I’d share it here.
If you find yourself in the situation where you can’t seem to drag and drop items. Try this trick to see if it works.
Left click on a random folder, don’t release it and press the escape button. You should hear the usual error beep from your speaker. Now try to drag and drop. Doing that should re-enable the drag and drop feature. Don’t know what caused it to disable. But this re-enables it regardless. 🙂
Hope this helps.
Credit goes to a forum post at thewindowsclub