1.Are there any bills/coins/foreign objects that have dropped in the cash drawer storage area?
Check that there are no bills/coins/foreign objects that have dropped in the cash drawer storage area.
2.Are there any object(s) on top that is in excess of the withstanding load?
If anything over the maximum withstanding load (8kg) is placed on top, it may prevent the cash drawer from closing. The surface in the front is not designed to withstand heavy weight. If an object is placed on top, then remove the object and try again.