drag and drop issue

After creating drag and drop pairs based on the instruction labeled at the drop and drag tolls it doesn't work.
In the "view" option the drag boxes are movable and can be placed to the correct places but the drag boxes are blank/empty.

Precisely:
After creating the drag-and-drop pairs according to the instructions for the drag and drop tools, the activity still doesn’t work.
In the “View” mode the drag boxes can be moved and placed in the correct positions, but the drag boxes appear blank/empty.